Connect4

[Rod]

Seven columns and six rows seems to be the defacto standard as does four in a row. So perhaps we should stick with that. Also who goes first should vary between games.

Description

This game is played on a vertical board which has seven hollow columns and six rows. Each column has a hole in the upper part of the board, where pieces are introduced. There is a window for every square, so that pieces can be seen from both sides.

In short, it´s a vertical board with 42 windows distributed in 6 rows and 7 columns.

Both players have a set of 21 thin pieces (like coins); each of them uses a different colour. The board is empty at the start of the game.

Objective

The aim for both players is to make a straight line of four own pieces; the line can be vertical, horizontal or diagonal.

How the game goes on

Before starting, players decide randomly which of them will be the beginner; moves are made alternatively, one by turn.

Moves entails in placing new pieces on the board; pieces slide downwards from upper holes, falling down to the last row or piling up on the last piece introduced in the same column. So, in every turn the introduced piece may be placed at most on seven different squares.

The winner is the first player who gets a straight line made with four own pieces and no gaps between them.

[B+]

Well I guess the question is best pointed to original makers of game. My reluctance with anything other that 8x8 is lack of symmetry which I equate to unfair game to player who has to go 2nd. Like Tic-tac-toe, a perfectly played game should end in draw.

[Rod]

That's exactly why the inventor created a 7x6 board. He wanted to ensure there would be a winner. He did not think people would like a game that could be drawn.

“The thing that intrigues me to this day, not being a mathematician, is that you would think a grid that has 42 spaces would stalemate often, but it doesn’t,” he says. “And that was my greatest fear. If it stalemated, I didn’t have a game, because you won’t want to play something and then say, ‘Oh, jeez, there’s no winner.’ How are you going to play a game that has no winner?”

[B+]

Well OK, so as long as the AI is the one to go 2nd we are fine! It could care less who wins but to be popular with humans it matters if you want them to enjoy the game more than a couple of times. So you have that carrot dangling before you, if you play perfectly, you will win.

[B+]

* decouple solving part from drawing part, so we can pitch AIs against one another

OK here are some brains to try and connect to a JB Interface. You guys can probably do it faster and better than I. I just got it working, found a trick it kept falling for, so I tweaked the scoring system and have yet to beat the thing now.

SUB AIMove
   ' What this sub does in English:
   ' This sub assigns the value to playing each column, then plays the best value with following caveats:
   ' + If it finds a winning move, it will play that immediately.
   ' + If it finds a spoiler move, it will play that if no winning move was found.
   ' + It will poisen the column's scoring, if opponent can play a winning move if AI plays this column,
   '   but it might be the only legal move left.  We will have to play it if no better score was found.

   'Global variables
   ' N is the Number of Columns and Rows of the grid
   ' NM1 = N - 1
   ' AIX = a legal column number to tell display sub what move the AI just made
   ' AIY = a legal row number  to tell display sub what move the AI just made
   ' WinX, WinY, WinD = These tell the display routine where the win is; WinD is the direction from WinX, WinY.
   ' Grid(NM1, NM1) = this is the game board array

   'REDIM SHARED DX(7), DY(7)  SHARED means Global
   ' DX(0) = 1: DY(0) = 0 '   : DString$(0) = "East"
   ' DX(1) = 1: DY(1) = 1 '   : DString$(1) = "South East"
   ' DX(2) = 0: DY(2) = 1 '   : DString$(2) = "South"
   ' DX(3) = -1: DY(3) = 1 '  : DString$(3) = "South West"
   ' DX(4) = -1: DY(4) = 0 '  : DString$(4) = "West"
   ' DX(5) = -1: DY(5) = -1 ' : DString$(5) = "North West"
   ' DX(6) = 0: DY(6) = -1 '  : DString$(6) = "North"
   ' DX(7) = 1: DY(7) = -1 '  : DString$(7) = "North East"


   ' This sub uses 3 assistent FUNCTIONs and the 3rd needs the CheckWin Function, so 4 supplementary FUNCTIONs

   'FUNCTION GetOpenRow (forCol)   ' if the forCol has an empty row, this returns the lowest, if filled it returns N.
   '    DIM i   ' <<< local to procedure
   '    GetOpenRow = N 'assume none open
   '    IF forCol < 0 OR forCol > NM1 THEN EXIT FUNCTION
   '    FOR i = NM1 TO 0 STEP -1
   '        IF Grid(forCol, i) = 0 THEN GetOpenRow = i: EXIT FUNCTION
   '    NEXT
   'END FUNCTION

   'FUNCTION GR (c, r) ' if c, r are out of bounds returns N else returns grid(c, r)
   '    ' need to check the grid(c, r) but only if c, r is on the board
   '    IF c < 0 OR c > NM1 OR r < 0 OR r > NM1 THEN GR = N ELSE GR = Grid(c, r)
   'END FUNCTION

   'FUNCTION Stupid (c, r)  '  returns -1 (true) if this (c, r) is played by AI it would be STUPID because opponent can win!
   '    DIM pr  ' <<< local to procedure
   '    Grid(c, r) = AI
   '    pr = GetOpenRow(c)
   '    IF pr <> N THEN
   '        Grid(c, pr) = P
   '        IF CheckWin = 4 THEN Stupid = -1
   '        Grid(c, pr) = 0
   '    END IF
   '    Grid(c, r) = 0
   'END FUNCTION

   'FUNCTION CheckWin
   '    DIM gridFull, r, c, s, i   ' <<< local to procedure
   '    ' return WinX, WinY, WinD along with +/- score, returns N  if grid full, 0 if no win and grid not full
   '    gridFull = N
   '    FOR r = NM1 TO 0 STEP -1 'bottom to top
   '        FOR c = 0 TO NM1
   '            IF Grid(c, r) THEN 'check if c starts a row
   '                IF c < NM1 - 2 THEN
   '                    s = 0
   '                    FOR i = 0 TO 3
   '                        s = s + Grid(c + i, r)
   '                    NEXT
   '                    IF s = 4 OR s = -4 THEN
   '                        WinX = c: WinY = r: WinD = 0
   '                        CheckWin = s: EXIT FUNCTION
   '                    END IF
   '                END IF
   '                IF r > 2 THEN 'check if c starts a col
   '                    s = 0
   '                    FOR i = 0 TO 3
   '                        s = s + Grid(c, r - i)
   '                    NEXT
   '                    IF s = 4 OR s = -4 THEN
   '                        WinX = c: WinY = r: WinD = 6 'north
   '                        CheckWin = s: EXIT FUNCTION
   '                    END IF
   '                END IF
   '                IF r > 2 AND c < NM1 - 2 THEN 'check if c starts diagonal up to right
   '                    s = 0
   '                    FOR i = 0 TO 3
   '                        s = s + Grid(c + i, r - i)
   '                    NEXT
   '                    IF s = 4 OR s = -4 THEN ' north  east
   '                        WinX = c: WinY = r: WinD = 7
   '                        CheckWin = s: EXIT FUNCTION
   '                    END IF
   '                END IF
   '                IF r > 2 AND c > 2 THEN 'check if c starts a diagonal up to left
   '                    s = 0
   '                    FOR i = 0 TO 3
   '                        s = s + Grid(c - i, r - i)
   '                    NEXT
   '                    IF s = 4 OR s = -4 THEN ' north west
   '                        WinX = c: WinY = r: WinD = 5
   '                        CheckWin = s: EXIT FUNCTION
   '                    END IF
   '                END IF
   '            ELSE
   '                gridFull = 0 ' at least one enpty cell left
   '            END IF 'grid is something
   '        NEXT
   '    NEXT
   '    CheckWin = gridFull
   'END FUNCTION


   ' these are the local variables for this SUB procedure
   DIM c, r, d, cntA, cntP, bestScore, startR, startC, iStep, test, goodF, i
   DIM openRow(NM1) ' find open rows once
   DIM scores(NM1) ' evaluate each column's potential
   AIX = -1: AIY = -1 ' set these when AI makes move, they are signal to display procedure AI's move.
   FOR c = 0 TO NM1
       openRow(c) = GetOpenRow(c)
       r = openRow(c)
       IF r <> N THEN
           FOR d = 0 TO 3 ' 4 directions to build connect 4's that use cell c, r
               startC = c + -3 * DX(d): startR = r + -3 * DY(d)
               FOR i = 0 TO 3 ' here we backup from the potential connect 4 in opposite build direction of c, r
                   cntA = 0: cntP = 0: goodF = -1 ' reset counts and flag for good connect 4
                   'from this start position run 4 steps forward to count all connects involving cell c, r
                   FOR iStep = 0 TO 3 ' process a potential connect 4
                       test = GR(startC + i * DX(d) + iStep * DX(d), startR + i * DY(d) + iStep * DY(d))
                       IF test = N THEN goodF = 0: EXIT FOR 'cant get connect4 from here
                       IF test = AI THEN cntA = cntA + 1
                       IF test = P THEN cntP = cntP + 1
                   NEXT iStep
                   IF goodF THEN 'evaluate the Legal Connect4 we could build with c, r
                       IF cntA = 3 THEN ' we are done!  winner!
                           AIX = c: AIY = r ' <<< this is the needed 4th cell to win tell ShowGrid last cell
                           Grid(c, r) = AI '  <<< this is the needed 4th cell to win, add to grid this is AI move
                           EXIT SUB
                       ELSEIF cntP = 3 THEN 'next best move spoiler!
                           AIX = c: AIY = r 'set the move but don't exit there might be a winner
                       ELSEIF cntA = 0 AND cntP = 2 THEN
                           scores(c) = scores(c) + 6
                       ELSEIF cntA = 2 AND cntP = 0 THEN ' very good offense or defense
                           scores(c) = scores(c) + 5 'play this to connect 3 or prevent player from Connect 3
                       ELSEIF cntA = 0 AND cntP = 1 THEN
                           scores(c) = scores(c) + 4
                       ELSEIF (cntA = 1 AND cntP = 0) OR (cntA = 0 AND cntP = 1) THEN 'good offense or defense
                           scores(c) = scores(c) + 3 ' play this to connect 2 or prevent player from Connect 2
                       ELSEIF (cntA = 0 AND cntP = 0) THEN ' OK it's not a wasted move as it has potential for connect4
                           scores(c) = scores(c) + 1 ' this is good move because this can still be a Connect 4
                       END IF
                   END IF ' in the board
               NEXT i
           NEXT d
           IF Stupid(c, r) THEN scores(c) = -1000 + scores(c) ' poison because if played the human can win
       END IF
   NEXT
   IF AIX <> -1 THEN ' we found a spoiler so move there since we haven't found a winner
       Grid(AIX, AIY) = AI ' make move on grid and done!
       EXIT SUB
   ELSE
       bestScore = -1000 ' a negative score indicates that the player can beat AI with their next move
       FOR c = 0 TO NM1
           r = openRow(c)
           IF r <> N THEN
               IF scores(c) > bestScore THEN bestScore = scores(c): AIY = r: AIX = c
           END IF
       NEXT
       IF AIX <> -1 THEN
           Grid(AIX, AIY) = AI ' make first best score move we found
       ELSE 'We have trouble!  Oh but it could be there are no moves!!!
           ' checkWin is run after every move by AI or Player if there were no legal moves left it should have caught that.
           ' Just in case it didn't here is an error stop!

           'note: LOCATE here is Row, Column the reverse of Just Basic
           BEEP: LOCATE 4, 2: PRINT "AI has failed to find a proper move, pess any to end..."
           SLEEP ' <<< pause until user presses a key
           END
       END IF
   END IF
END SUB

BTW, this is complete rewrite from code I posted earlier here is the EXE.

Attachments:

Connect4 8x8 2020 update.zip (819.39 KB)

[B+]

Maybe this is what I have to settle for?

[Rod]

I see AI and P used as if they are set global but dont see where that is happening or where they are set? function stupid.

[B+]

Dec 14, 2020 14:08:42 GMT Rod said:

I see AI and P used as if they are set global but dont see where that is happening or where they are set? function stupid.

I just have the brain ready to transplant into JB interface, notes covering the transplant are included at the beginning of the Sub comments which actually say AI and P are Global (Constants actually equal -1 and 1 respectively).

I should get to building the interface and translating this sub to JB later today. The hard part is done and working.

[Rod]

Still can't see that in the code you posted. I was trying to convert to a 7x6 grid. Never mind will wait for your interface.

[B+]

Almost there! (a little rusty and spoiled by another IDE)

Big Game tonight, hope to finish before it starts ;-))

[B+]

Just finishing up, but they are finding cracks in the AI at another forum.

[B+]

OK got it before the Game!

' 8x8 Connect 4 by B+ port to JB 2020-12-14

global SQ, SW, SH, N, NM1, P, AI, XO, YO                  ' True CONSTants
global GameOn, GoFirst, Turn, AIX, AIY, WinX, WinY, WinD  ' for sharing with subroutines
global Kee$, MouseX, MouseY                               ' input from keyboard or left mouse click
SQ = 60           ' square or grid cell
N = 8             ' number of rows and columns  OK now works for 7x7 or 8x8
SW = SQ * (N + 2) ' screen width
SH = SQ * (N + 3) ' screen height
NM1 = N - 1       ' N minus 1
P = 1             ' Player is 1 on grid
AI = -1           ' AI is -1 on grid
XO = SQ           ' x offset for grid
YO = 2 * SQ       ' y offset for grid

dim Grid(NM1, NM1)  ' = this is the game board array
dim DX(7),   DY(7)  ' Direction Changes in x, y or col, row
DX(0) =  1:  DY(0) =  0 '  : DString$(0) = "East"
DX(1) =  1:  DY(1) =  1 '  : DString$(1) = "South East"
DX(2) =  0:  DY(2) =  1 '  : DString$(2) = "South"
DX(3) = -1:  DY(3) =  1 '  : DString$(3) = "South West"
DX(4) = -1:  DY(4) =  0 '  : DString$(4) = "West"
DX(5) = -1:  DY(5) = -1 '  : DString$(5) = "North West"
DX(6) =  0:  DY(6) = -1 '  : DString$(6) = "North"
DX(7) =  1:  DY(7) = -1 '  : DString$(7) = "North East"

' Needed for AImove processing
dim openRow(NM1) ' find open rows once
dim Scores(NM1)  ' evaluate each column's potential

nomainwin
WindowWidth = SW + 8
WindowHeight = SH + 32
UpperLeftX = (1200 - SW) / 2
UpperLeftY = (700 - SH) / 2
open "8x8 Connect 4 with AI by B+ " for graphics_nsb_nf as #gr
#gr "setfocus"
#gr "trapclose Quit"
#gr "when leftButtonUp LButtonUp"
#gr "when characterInput CharIn"
#gr "down"
#gr "fill black"

GameOn = -1: GoFirst = AI: Turn = AI: MouseX = -1 : MouseY = -1
call ShowGrid
while GameOn
   if Turn = P then
       if MouseX <> -1 then 'must have clicked the screen
           if (MouseX - XO) > 0 and (MouseY - YO) > 0 then
               row = INT((MouseY - YO) / SQ): col = INT((MouseX - XO) / SQ)
               if col >= 0 and col <= NM1 and row >= 0 and row <= NM1 then
                   r = GetOpenRow(col) 'find next space open on board
                   if r <> N then
                       Grid(col, r) = P
                       Turn = AI
                   end if
               end if
           end if
           MouseX = -1 : MouseY = -1
       end if
   else
       call AIMove
       Turn = P
   end if
   call ShowGrid
   call Pause 200
wend
wait

sub AIMove
   ' What this sub does in English:
   ' This sub assigns the value to playing each column, then plays the best value with following caveats:
   ' + If it finds a winning move, it will play that immediately.
   ' + If it finds a spoiler move, it will play that if no winning move was found.
   ' + It will poisen the column's scoring, if opponent can play a winning move if AI plays this column,
   '   but it might be the only legal move left.  We will have to play it if no better score was found.
   dim Scores(NM1)
   AIX = -1: AIY = -1 ' set these when AI makes move, they are signal to display procedure AI's move.
   for c = 0 to NM1
       openRow(c) = GetOpenRow(c)
       r = openRow(c)
       if r <> N then
           for d = 0 to 3 ' 4 directions to build connect 4's that use cell c, r
               startC = c + -3 * DX(d): startR = r + -3 * DY(d)
               for i = 0 to 3 ' here we backup from the potential connect 4 in opposite build direction of c, r
                   cntA = 0: cntP = 0: goodF = -1 ' reset counts and flag for good connect 4
                   'from this start position run 4 steps forward to count all connects involving cell c, r
                   for iStep = 0 to 3 ' process a potential connect 4
                       test = GR(startC + i * DX(d) + iStep * DX(d), startR + i * DY(d) + iStep * DY(d))
                       if test = N then goodF = 0: exit for 'cant get connect4 from here
                       if test = AI then cntA = cntA + 1
                       if test = P then cntP = cntP + 1
                   next iStep
                   if goodF then 'evaluate the Legal Connect4 we could build with c, r
                       if cntA = 3 then ' we are done!  winner!
                           AIX = c: AIY = r ' <<< this is the needed 4th cell to win tell ShowGrid last cell
                           Grid(c, r) = AI '  <<< this is the needed 4th cell to win, add to grid this is AI move
                           exit sub
                       else
                           if cntP = 3 then 'next best move spoiler!
                               AIX = c: AIY = r 'set the move but don't exit there might be a winner
                           else
                               if cntA = 0 and cntP = 2 then
                                   Scores(c) = Scores(c) + 8
                               else
                                   if cntA = 2 and cntP = 0 then ' very good offense or defense
                                       Scores(c) = Scores(c) + 6 'play this to connect 3 or prevent player from Connect 3
                                   else
                                       if cntA = 0 and cntP = 1 then
                                           Scores(c) = Scores(c) + 7
                                       else
                                           if cntA = 1 and cntP = 0 then 'good offense or defense
                                               Scores(c) = Scores(c) + 5 ' play this to connect 2 or prevent player from Connect 2
                                           else
                                               if (cntA = 0 and cntP = 0) then ' OK it's not a wasted move as it has potential for connect4
                                                   Scores(c) = Scores(c) + 1 ' this is good move because this can still be a Connect 4
                                               end if
                                           end if
                                       end if
                                   end if
                               end if
                           end if
                       end if
                   end if ' in the board
               next i
           next d
           if Stupid(c, r) then Scores(c) = -1000 + Scores(c) ' poison because if played the human can win
       end if
   next
   if AIX <> -1 then ' we found a spoiler so move there since we haven't found a winner
       Grid(AIX, AIY) = AI ' make move on grid and done!
       exit sub
   else
       bestScore = -1000 ' a negative score indicates that the player can beat AI with their next move
       for c = 0 to NM1
           r = openRow(c)
           if r <> N then
               if Scores(c) > bestScore then bestScore = Scores(c): AIY = r: AIX = c
           end if
       next
       if AIX <> -1 then
           Grid(AIX, AIY) = AI ' make first best score move we found
       else 'We have trouble!  Oh but it could be there are no moves!!!
           ' checkWin is run after every move by AI or Player if there were no legal moves left it should have caught that.
           ' Just in case it didn't here is an error stop!
           notice "sub AImove failed to find a move to make. Calling it quits."
           call Quit "gr"
       end if
   end if
end sub

function GetOpenRow (forCol) ' if the forCol has an empty row, this returns the lowest, if filled it returns N.
   GetOpenRow = N 'assume none open
   if forCol < 0 or forCol > NM1 then exit function
   for i = NM1 to 0 STEP -1
       if Grid(forCol, i) = 0 then GetOpenRow = i: exit function
   next
end function

function GR (c, r) ' if c, r are out of bounds returns N else returns grid(c, r)
   ' need to check the grid(c, r) but only if c, r is on the board, if NOT return N
   if c < 0 or c > NM1 or r < 0 or r > NM1 then GR = N else GR = Grid(c, r)
end function

function Stupid (c, r) '  returns -1 (true) if this (c, r) is played by AI it would be STUPID because opponent can win!
   Grid(c, r) = AI
   pr = GetOpenRow(c)
   if pr <> N then
       Grid(c, pr) = P
       if CheckWin() = 4 then Stupid = -1
       Grid(c, pr) = 0
   end if
   Grid(c, r) = 0
end function

function CheckWin() 'return WinX, WinY, WinD along with +/- score, returns N  if grid full, 0 if no win and grid not full
   gridFull = N
   for r = NM1 to 0 STEP -1 'bottom to top
       for c = 0 to NM1
           if Grid(c, r) then 'check if c starts a row
               if c < NM1 - 2 then
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c + i, r)
                   next
                   if s = 4 or s = -4 then
                       WinX = c: WinY = r: WinD = 0
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 then 'check if c starts a col
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c, r - i)
                   next
                   if s = 4 or s = -4 then
                       WinX = c: WinY = r: WinD = 6 'north
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 and c < NM1 - 2 then 'check if c starts diagonal up to right
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c + i, r - i)
                   next
                   if s = 4 or s = -4 then ' north  east
                       WinX = c: WinY = r: WinD = 7
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 and c > 2 then 'check if c starts a diagonal up to left
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c - i, r - i)
                   next
                   if s = 4 or s = -4 then ' north west
                       WinX = c: WinY = r: WinD = 5
                       CheckWin = s: exit function
                   end if
               end if
           else
               gridFull = 0 ' at least one empty cell left
           end if 'grid is something
       next
   next
   CheckWin = gridFull
end function

sub ShowGrid
   #gr "fill black"
   #gr "color green"
   for i = 0 to N 'grid
       #gr "line ";SQ * i + XO;" ";YO;" ";SQ * i + XO;" ";YO + N * SQ
       #gr "line ";XO;" ";SQ * i + YO;" ";XO + N * SQ;" ";SQ * i + YO
   next
   for r = NM1 to 0 STEP -1 'plays
       for c = 0 to NM1
           if Grid(c, r) = P then
               #gr "color red"
               #gr "backcolor red"
           else
               if Grid(c, r) = AI then
                   if c = AIX and r = AIY then 'highlite last AI move
                       #gr "color ";125;" ";125;" ";255
                       #gr "backcolor ";125;" ";125;" ";255
                   else
                       #gr "color blue"
                       #gr "backcolor blue"
                   end if
               end if
           end if
           if Grid(c, r) then
               #gr "place ";c * SQ + XO + 3;" ";r * SQ + YO + 3
               #gr "boxfilled ";c * SQ + XO + 3 + SQ - 6;" ";r * SQ + YO + 3 + SQ - 6
           end if
       next
   next
   check = CheckWin()
   if check then 'report end of round and see if want to play again
       if check = 4 or check = -4 then
           #gr "color white"
           for i = 0 to 3
               #gr "place ";(WinX + i * DX(WinD)) * SQ + XO + 5;" ";(WinY + i * DY(WinD)) * SQ + YO + 5
               #gr "box ";(WinX + i * DX(WinD)) * SQ + XO + 5 + SQ - 10;" ";(WinY + i * DY(WinD)) * SQ + YO + 5 + SQ - 10
           next
       end if
       if check = -4 then
           s$ = "AI is Winner!"
       else
           if check = 4 then
               s$ = "Human is Winner!"
           else
               if check = N then
                   s$ = "Board is full, no winner." ' keep Turn the same
               end if
           end if
       end if
       #gr "color white"
       #gr "backcolor black"
       call CText 32, s$
       Kee$ = ""
       call CText 64, "Play again? just press spacebar, quit with any other."
       while len(Kee$) = 0 : scan : wend
       if Kee$ = " " then
           dim Grid(NM1, NM1)
           if GoFirst = P then GoFirst = AI else GoFirst = P
           Turn = GoFirst
       else
          GameOn = 0
          notice "Goodbye!"
       end if
   end if
end sub

sub Text x, y, message$ 'note: have to reset fore or back color after ink
   #gr "place ";x;" ";y;";|";message$
end sub

sub CText y, message$ ' center text on lower left? y pixel
   call Text (SW - len(message$) * 7) / 2, y, message$
end sub

sub LButtonUp H$, mx, my  'must have handle and mouse x,y
   MouseX = mx : MouseY = my
end sub

sub CharIn H$, c$
   Kee$ = c$
end sub

sub Quit H$
   close #gr
   end
end sub

sub Pause mil   'tsh version has scan built-in
   t0 = time$("ms")
   while time$("ms") < t0 + mil : scan : wend
end sub



EDIT: for both 7x7 and 8x8 or 9x9 or more or less

[B+]

OK now that I have it ported, here is a mod with NumRows and NumCols so you can do any size board within reason.
' Connect 4 NumRows & Cols by B+ port to JB 2020-12-15

global SQ, SW, SH, NumCols, NCM1, NumRows, NRM1, P, AI, XO, YO  ' True CONSTants
global GameOn, GoFirst, Turn, AIX, AIY, WinX, WinY, WinD        ' for sharing with subroutines
global Kee$, MouseX, MouseY                                     ' input from keyboard or left mouse click
SQ = 60           ' square or grid cell pixel size
NumCols = 7
NumRows = 6
SW = SQ * (NumCols + 2) ' screen width
SH = SQ * (NumRows + 3) ' screen height
NCM1 = NumCols - 1      ' NumCols minus 1
NRM1 = NumRows - 1      ' NumRows minus 1
P = 1             ' Player is 1 on grid
AI = -1           ' AI is -1 on grid
XO = SQ           ' x offset for grid
YO = 2 * SQ       ' y offset for grid

dim Grid(NCM1, NRM1)  ' = this is the game board array
dim DX(7),   DY(7)  ' Direction Changes in x, y or col, row
DX(0) =  1:  DY(0) =  0 '  : DString$(0) = "East"
DX(1) =  1:  DY(1) =  1 '  : DString$(1) = "South East"
DX(2) =  0:  DY(2) =  1 '  : DString$(2) = "South"
DX(3) = -1:  DY(3) =  1 '  : DString$(3) = "South West"
DX(4) = -1:  DY(4) =  0 '  : DString$(4) = "West"
DX(5) = -1:  DY(5) = -1 '  : DString$(5) = "North West"
DX(6) =  0:  DY(6) = -1 '  : DString$(6) = "North"
DX(7) =  1:  DY(7) = -1 '  : DString$(7) = "North East"

' Needed for AImove processing
dim openRow(NCM1) ' find open rows once
dim Scores(NCM1)  ' evaluate each column's potential

nomainwin
WindowWidth = SW + 8
WindowHeight = SH + 32
UpperLeftX = (1200 - SW) / 2
UpperLeftY = (700 - SH) / 2
open "Connect 4: ";NumCols;"x";NumRows;" with AI by B+ " for graphics_nsb_nf as #gr
#gr "setfocus"
#gr "trapclose Quit"
#gr "when leftButtonUp LButtonUp"
#gr "when characterInput CharIn"
#gr "down"
#gr "fill black"

GameOn = -1: GoFirst = AI: Turn = AI: MouseX = -1 : MouseY = -1
call ShowGrid
while GameOn
   if Turn = P then
       if MouseX <> -1 then 'must have clicked the screen
           if (MouseX - XO) > 0 and (MouseY - YO) > 0 then
               row = INT((MouseY - YO) / SQ): col = INT((MouseX - XO) / SQ)
               if col >= 0 and col <= NCM1 and row >= 0 and row <= NRM1 then
                   r = GetOpenRow(col) 'find next space open on board
                   if r <> NumRows then
                       Grid(col, r) = P
                       Turn = AI
                   end if
               end if
           end if
           MouseX = -1 : MouseY = -1
       end if
   else
       call AIMove
       Turn = P
   end if
   call ShowGrid
   call Pause 200
wend
wait

sub AIMove
   ' What this sub does in English:
   ' This sub assigns the value to playing each column, then plays the best value with following caveats:
   ' + If it finds a winning move, it will play that immediately.
   ' + If it finds a spoiler move, it will play that if no winning move was found.
   ' + It will poisen the column's scoring, if opponent can play a winning move if AI plays this column,
   '   but it might be the only legal move left.  We will have to play it if no better score was found.
   dim Scores(NCM1)
   AIX = -1: AIY = -1 ' set these when AI makes move, they are signal to display procedure AI's move.
   for c = 0 to NCM1
       openRow(c) = GetOpenRow(c)
       r = openRow(c)
       if r <> NumRows then
           for d = 0 to 3 ' 4 directions to build connect 4's that use cell c, r
               startC = c + -3 * DX(d): startR = r + -3 * DY(d)
               for i = 0 to 3 ' here we backup from the potential connect 4 in opposite build direction of c, r
                   cntA = 0: cntP = 0: goodF = -1 ' reset counts and flag for good connect 4
                   'from this start position run 4 steps forward to count all connects involving cell c, r
                   for iStep = 0 to 3 ' process a potential connect 4
                       test = GR(startC + i * DX(d) + iStep * DX(d), startR + i * DY(d) + iStep * DY(d))
                       if test = NumRows then goodF = 0: exit for 'cant get connect4 from here
                       if test = AI then cntA = cntA + 1
                       if test = P then cntP = cntP + 1
                   next iStep
                   if goodF then 'evaluate the Legal Connect4 we could build with c, r
                       if cntA = 3 then ' we are done!  winner!
                           AIX = c: AIY = r ' <<< this is the needed 4th cell to win tell ShowGrid last cell
                           Grid(c, r) = AI '  <<< this is the needed 4th cell to win, add to grid this is AI move
                           exit sub
                       else
                           if cntP = 3 then 'next best move spoiler!
                               AIX = c: AIY = r 'set the move but don't exit there might be a winner
                           else
                               if cntA = 0 and cntP = 2 then
                                   Scores(c) = Scores(c) + 8
                               else
                                   if cntA = 2 and cntP = 0 then ' very good offense or defense
                                       Scores(c) = Scores(c) + 6 'play this to connect 3 or prevent player from Connect 3
                                   else
                                       if cntA = 0 and cntP = 1 then
                                           Scores(c) = Scores(c) + 7
                                       else
                                           if cntA = 1 and cntP = 0 then 'good offense or defense
                                               Scores(c) = Scores(c) + 5 ' play this to connect 2 or prevent player from Connect 2
                                           else
                                               if (cntA = 0 and cntP = 0) then ' OK it's not a wasted move as it has potential for connect4
                                                   Scores(c) = Scores(c) + 1 ' this is good move because this can still be a Connect 4
                                               end if
                                           end if
                                       end if
                                   end if
                               end if
                           end if
                       end if
                   end if ' in the board
               next i
           next d
           if Stupid(c, r) then Scores(c) = -1000 + Scores(c) ' poison because if played the human can win
       end if
   next
   if AIX <> -1 then ' we found a spoiler so move there since we haven't found a winner
       Grid(AIX, AIY) = AI ' make move on grid and done!
       exit sub
   else
       bestScore = -1000 ' a negative score indicates that the player can beat AI with their next move
       for c = 0 to NCM1
           r = openRow(c)
           if r <> NumRows then
               if Scores(c) > bestScore then bestScore = Scores(c): AIY = r: AIX = c
           end if
       next
       if AIX <> -1 then
           Grid(AIX, AIY) = AI ' make first best score move we found
       else 'We have trouble!  Oh but it could be there are no moves!!!
           ' checkWin is run after every move by AI or Player if there were no legal moves left it should have caught that.
           ' Just in case it didn't here is an error stop!
           notice "sub AImove failed to find a move to make. Calling it quits."
           call Quit "gr"
       end if
   end if
end sub

function GetOpenRow (forCol) ' if the forCol has an empty row, this returns the lowest, if filled it returns N.
   GetOpenRow = NumRows 'assume none open
   if forCol < 0 or forCol > NCM1 then exit function
   for i = NRM1 to 0 STEP -1
       if Grid(forCol, i) = 0 then GetOpenRow = i: exit function
   next
end function

function GR (c, r) ' if c, r are out of bounds returns N else returns grid(c, r)
   ' need to check the grid(c, r) but only if c, r is on the board, if NOT return N
   if c < 0 or c > NCM1 or r < 0 or r > NRM1 then GR = NumRows else GR = Grid(c, r)
end function

function Stupid (c, r) '  returns -1 (true) if this (c, r) is played by AI it would be STUPID because opponent can win!
   Grid(c, r) = AI
   pr = GetOpenRow(c)
   if pr <> NumRows then
       Grid(c, pr) = P
       if CheckWin() = 4 then Stupid = -1
       Grid(c, pr) = 0
   end if
   Grid(c, r) = 0
end function

function CheckWin() 'return WinX, WinY, WinD along with +/- score, returns N  if grid full, 0 if no win and grid not full
   gridFull = NumRows
   for r = NRM1 to 0 STEP -1 'bottom to top
       for c = 0 to NCM1
           if Grid(c, r) then 'check if c starts a row
               if c < NCM1 - 2 then
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c + i, r)
                   next
                   if s = 4 or s = -4 then
                       WinX = c: WinY = r: WinD = 0
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 then 'check if c starts a col
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c, r - i)
                   next
                   if s = 4 or s = -4 then
                       WinX = c: WinY = r: WinD = 6 'north
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 and c < NCM1 - 2 then 'check if c starts diagonal up to right
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c + i, r - i)
                   next
                   if s = 4 or s = -4 then ' north  east
                       WinX = c: WinY = r: WinD = 7
                       CheckWin = s: exit function
                   end if
               end if
               if r > 2 and c > 2 then 'check if c starts a diagonal up to left
                   s = 0
                   for i = 0 to 3
                       s = s + Grid(c - i, r - i)
                   next
                   if s = 4 or s = -4 then ' north west
                       WinX = c: WinY = r: WinD = 5
                       CheckWin = s: exit function
                   end if
               end if
           else
               gridFull = 0 ' at least one empty cell left
           end if 'grid is something
       next
   next
   CheckWin = gridFull
end function

sub ShowGrid
   #gr "fill black"
   #gr "color green"
   for i = 0 to NumCols 'grid
       #gr "line ";SQ * i + XO;" ";YO;" ";SQ * i + XO;" ";YO + NumRows * SQ
   next
   for i = 0 to NumRows
       #gr "line ";XO;" ";SQ * i + YO;" ";XO + NumCols * SQ;" ";SQ * i + YO
   next
   for r = NRM1 to 0 STEP -1 'plays
       for c = 0 to NCM1
           if Grid(c, r) = P then
               #gr "color red"
               #gr "backcolor red"
           else
               if Grid(c, r) = AI then
                   if c = AIX and r = AIY then 'highlite last AI move
                       #gr "color ";125;" ";125;" ";255
                       #gr "backcolor ";125;" ";125;" ";255
                   else
                       #gr "color blue"
                       #gr "backcolor blue"
                   end if
               end if
           end if
           if Grid(c, r) then
               #gr "place ";c * SQ + XO + 3;" ";r * SQ + YO + 3
               #gr "boxfilled ";c * SQ + XO + 3 + SQ - 6;" ";r * SQ + YO + 3 + SQ - 6
           end if
       next
   next
   check = CheckWin()
   if check then 'report end of round and see if want to play again
       if check = 4 or check = -4 then
           #gr "color white"
           for i = 0 to 3
               #gr "place ";(WinX + i * DX(WinD)) * SQ + XO + 5;" ";(WinY + i * DY(WinD)) * SQ + YO + 5
               #gr "box ";(WinX + i * DX(WinD)) * SQ + XO + 5 + SQ - 10;" ";(WinY + i * DY(WinD)) * SQ + YO + 5 + SQ - 10
           next
       end if
       if check = -4 then
           s$ = "AI is Winner!"
       else
           if check = 4 then
               s$ = "Human is Winner!"
           else
               if check = N then
                   s$ = "Board is full, no winner." ' keep Turn the same
               end if
           end if
       end if
       #gr "color white"
       #gr "backcolor black"
       call CText 32, s$
       Kee$ = ""
       call CText 64, "Play again? just press spacebar, quit with any other."
       while len(Kee$) = 0 : scan : wend
       if Kee$ = " " then
           dim Grid(NCM1, NRM1)
           if GoFirst = P then GoFirst = AI else GoFirst = P
           Turn = GoFirst
       else
          GameOn = 0
          notice "Goodbye!"
       end if
   end if
end sub

sub Text x, y, message$ 'note: have to reset fore or back color after ink
   #gr "place ";x;" ";y;";|";message$
end sub

sub CText y, message$ ' center text on lower left? y pixel
   call Text (SW - len(message$) * 7) / 2, y, message$
end sub

sub LButtonUp H$, mx, my  'must have handle and mouse x,y
   MouseX = mx : MouseY = my
end sub

sub CharIn H$, c$
   Kee$ = c$
end sub

sub Quit H$
   close #gr
   end
end sub

sub Pause mil   'tsh version has scan built-in
   t0 = time$("ms")
   while time$("ms") < t0 + mil : scan : wend
end sub


When I was testing this the AI made a "Stupid" move (see FUNCTION Stupid, I always wanted to write a Stupid FUNCTION ) which means there may be trouble in Emerald City. I hadn't seen any Stupid moves made by AI in the square grids so there may be a subtle error maybe in the CheckWin FUNCTION which helps decide a Stupid move. CheckWin was definitely based on a square grid.

PS really great game 47 to 42 too bad Browns lost, but dang! what a game.

[B+]

An update access for assessing how the AI is scoring, a move by move accounting at the end of a game and of course prettier colors ;-))
This might suggest ideas for tweaking the AI to make it stronger.

' Connect 4 Any Rows and Cols 2020-12-17.txt  B+

global SQ, SW, SH, NumCols, NCM1, NumRows, NRM1, P, AI, XO, YO  ' True CONSTants
global GameOn, GoFirst, Turn, AIX, AIY, WinX, WinY, WinD        ' for sharing with subroutines
global Kee$, MouseX, MouseY
global PlayerLastMoveCol, PlayerLastMoveRow, MoveNum, LastMoveNum
SQ = 60           ' square or grid cell pixel size
NumCols = 8
NumRows = 8
SW = SQ * (NumCols + 2) ' screen width
SH = SQ * (NumRows + 3) ' screen height
NCM1 = NumCols - 1      ' NumCols minus 1
NRM1 = NumRows - 1      ' NumRows minus 1
P = 1             ' Player is 1 on grid
AI = -1           ' AI is -1 on grid
XO = SQ           ' x offset for grid
YO = 2 * SQ       ' y offset for grid

dim Grid(NCM1, NRM1)  ' = this is the game board array
dim DX(7),   DY(7)  ' Direction Changes in x, y or col, row
DX(0) =  1:  DY(0) =  0 '  : DString$(0) = "East"
DX(1) =  1:  DY(1) =  1 '  : DString$(1) = "South East"
DX(2) =  0:  DY(2) =  1 '  : DString$(2) = "South"
DX(3) = -1:  DY(3) =  1 '  : DString$(3) = "South West"
DX(4) = -1:  DY(4) =  0 '  : DString$(4) = "West"
DX(5) = -1:  DY(5) = -1 '  : DString$(5) = "North West"
DX(6) =  0:  DY(6) = -1 '  : DString$(6) = "North"
DX(7) =  1:  DY(7) = -1 '  : DString$(7) = "North East"

' Needed for AImove processing
dim OpenRow(NCM1) ' find open rows once
dim Scores(NCM1)  ' evaluate each column's potential
dim Record$(NCM1, NRM1) ' forrecord moves

nomainwin
WindowWidth = SW + 8
WindowHeight = SH + 32
UpperLeftX = (1200 - SW) / 2
UpperLeftY = (700 - SH) / 2
open "Connect 4: ";NumCols;"x";NumRows;" with AI by B+ " for graphics_nsb_nf as #gr
#gr "setfocus"
#gr "trapclose Quit"
#gr "when leftButtonUp LButtonUp"
#gr "when characterInput CharIn"
#gr "down"
#gr "fill black"

GameOn = -1: GoFirst = AI: Turn = AI: MouseX = -1 : MouseY = -1
call ShowGrid
while GameOn
   if Turn = P then
       if MouseX <> -1 then 'must have clicked the screen
           if (MouseX - XO) > 0 and (MouseY - YO) > 0 then
               row = INT((MouseY - YO) / SQ): col = INT((MouseX - XO) / SQ)
               if col >= 0 and col <= NCM1 and row >= 0 and row <= NRM1 then
                   r = GetOpenRow(col) 'find next space open on board
                   if r <> NumRows then
                       Grid(col, r) = P: Turn = AI: PlayerLastMoveCol = col: PlayerLastMoveRow = r: MoveNum = MoveNum + 1
                   end if
               end if
           end if
           MouseX = -1 : MouseY = -1
       end if
   else
       call AIMove
        Turn = P: MoveNum = MoveNum + 1
   end if
   call ShowGrid
   call Pause 200
wend
wait

sub AIMove
   ' What this sub does in English:
   ' This sub assigns the value to playing each column, then plays the best value with following caveats:
   ' + If it finds a winning move, it will play that immediately.
   ' + If it finds a spoiler move, it will play that if no winning move was found.
   ' + It will poisen the column's scoring, if opponent can play a winning move if AI plays this column,
   '   but it might be the only legal move left.  We will have to play it if no better score was found.
   dim Scores(NCM1)
   AIX = -1: AIY = -1 ' set these when AI makes move, they are signal to display procedure AI's move.
   for c = 0 to NCM1
       OpenRow(c) = GetOpenRow(c)
       r = OpenRow(c)
       if r <> NumRows then
           for d = 0 to 3 ' 4 directions to build connect 4's that use cell c, r
               startC = c + -3 * DX(d): startR = r + -3 * DY(d)
               for i = 0 to 3 ' here we backup from the potential connect 4 in opposite build direction of c, r
                   cntA = 0: cntP = 0: goodF = -1 ' reset counts and flag for good connect 4
                   'from this start position run 4 steps forward to count all connects involving cell c, r
                   for iStep = 0 to 3 ' process a potential connect 4
                       test = GR(startC + i * DX(d) + iStep * DX(d), startR + i * DY(d) + iStep * DY(d))
                       if test = NumRows then goodF = 0: exit for 'cant get connect4 from here
                       if test = AI then cntA = cntA + 1
                       if test = P then cntP = cntP + 1
                   next iStep
                   if goodF then 'evaluate the Legal Connect4 we could build with c, r
                       if cntA = 3 then ' we are done!  winner!
                           AIX = c: AIY = r ' <<< this is the needed 4th cell to win tell ShowGrid last cell
                           Grid(c, r) = AI '  <<< this is the needed 4th cell to win, add to grid this is AI move
                           Scores(c) = Scores(c) + 1000
                           exit sub
                       else
                           if cntP = 3 then 'next best move spoiler!
                               AIX = c: AIY = r 'set the move but don't exit there might be a winner
                               Scores(c) = Scores(c) + 900
                           else
                               if cntA = 0 and cntP = 2 then
                                   Scores(c) = Scores(c) + 8
                               else
                                   if cntA = 2 and cntP = 0 then ' very good offense or defense
                                       Scores(c) = Scores(c) + 4 'play this to connect 3 or prevent player from Connect 3
                                   else
                                       if cntA = 0 and cntP = 1 then
                                           Scores(c) = Scores(c) + 4
                                       else
                                           if cntA = 1 and cntP = 0 then 'good offense or defense
                                               Scores(c) = Scores(c) + 2 ' play this to connect 2 or prevent player from Connect 2
                                           else
                                               if cntA = 0 and cntP = 0 then ' OK it's not a wasted move as it has potential for connect4
                                                   Scores(c) = Scores(c) + 1 ' this is good move because this can still be a Connect 4
                                               end if
                                           end if
                                       end if
                                   end if
                               end if
                           end if
                       end if
                   end if ' in the board
               next i
           next d
           if Stupid(c, r) then Scores(c) = -1000 + Scores(c) ' poison because if played the human can win
       end if
   next
   if AIX <> -1 then ' we found a spoiler so move there since we haven't found a winner
       Grid(AIX, AIY) = AI ' make move on grid and done!
       exit sub
   else
       if GetOpenRow(PlayerLastMoveCol) < NumRows then 'all things being equal play on top of player's last move
           bestScore = Scores(PlayerLastMoveCol): AIY = PlayerLastMoveRow - 1: AIX = PlayerLastMoveCol
       else
           bestScore = -1000 ' a negative score indicates that the player can beat AI with their next move
       end if
       for c = 0 to NCM1
           r = OpenRow(c)
           if r <> NumRows then
               if Scores(c) > bestScore then bestScore = Scores(c): AIY = r: AIX = c
           end if
       next
       if AIX <> -1 then
           Grid(AIX, AIY) = AI ' make first best score move we found
       else 'We have trouble!  Oh but it could be there are no moves!!!
           ' checkWin is run after every move by AI or Player if there were no legal moves left it should have caught that.
           ' Just in case it didn't here is an error stop!
           notice "sub AImove failed to find a move to make. Calling it quits."
           call Quit "gr"
       end if
   end if
end sub

function GetOpenRow (forCol) ' if the forCol has an empty row, this returns the lowest, if filled it returns N.
   GetOpenRow = NumRows 'assume none open
   if forCol < 0 or forCol > NCM1 then exit function
   for i = NRM1 to 0 STEP -1
       if Grid(forCol, i) = 0 then GetOpenRow = i: exit function
   next
end function

function GR (c, r) ' if c, r are out of bounds returns N else returns grid(c, r)
   ' need to check the grid(c, r) but only if c, r is on the board, if NOT return N
   if c < 0 or c > NCM1 or r < 0 or r > NRM1 then GR = NumRows else GR = Grid(c, r)
end function

function Stupid (c, r) '  returns -1 (true) if this (c, r) is played by AI it would be STUPID because opponent can win!
   Grid(c, r) = AI
   pr = GetOpenRow(c)
   if pr <> NumRows then
       Grid(c, pr) = P
       if CheckWin() = 4 then Stupid = -1
       Grid(c, pr) = 0
   end if
   Grid(c, r) = 0
end function

function CheckWin() 'return WinX, WinY, WinD along with +/- score, returns N  if grid full, 0 if no win and grid not full
   gridFull = NumRows
   for r = NRM1 to 0 STEP -1 'bottom to top
       for c = 0 to NCM1
           if Grid(c, r) then 'check if c starts a row
               if c < NCM1 - 2 then
                   s = 0
                   for i = 0 to 3 'east
                       s = s + Grid(c + i, r)
                   next
                   if s = 4 or s = -4 then WinX = c: WinY = r: WinD = 0: CheckWin = s: exit function
               end if
               if r > 2 then 'check if c starts a col
                   s = 0
                   for i = 0 to 3 'north
                       s = s + Grid(c, r - i)
                   next
                   if s = 4 or s = -4 then WinX = c: WinY = r: WinD = 6: CheckWin = s: exit function
               end if
               if r > 2 and c < NCM1 - 2 then 'check if c starts diagonal up to right
                   s = 0
                   for i = 0 to 3 ' north  east
                       s = s + Grid(c + i, r - i)
                   next
                   if s = 4 or s = -4 then WinX = c: WinY = r: WinD = 7: CheckWin = s: exit function
               end if
               if r > 2 and c > 2 then 'check if c starts a diagonal up to left
                   s = 0
                   for i = 0 to 3  ' north west
                       s = s + Grid(c - i, r - i)
                   next
                   if s = 4 or s = -4 then WinX = c: WinY = r: WinD = 5: CheckWin = s: exit function
               end if
           else
               gridFull = 0 ' at least one empty cell left
           end if 'grid is something
       next
   next
   CheckWin = gridFull
end function

sub ShowGrid
   Browns$ = 255;" ";34;" ";0
   Ravens$ = 57;" ";0;" ";39
   if MoveNum <> lastMoveNum then ' file newest move
       if MoveNum = 1 then dim Record$(NCM1, NRM1)
       if Turn = -1 then
           Record$(PlayerLastMoveCol, PlayerLastMoveRow) = MoveNum;" ";"P"
       else
           Record$(AIX, AIY) = MoveNum;" ";"A"
       end if
       lastMoveNum = MoveNum
   end if
   #gr "fill black"
   #gr "color ";0;" ";68;" ";0
   #gr "backcolor ";0;" ";68;" ";0
   #gr "place ";XO;" ";YO
   #gr "boxfilled ";NumCols * SQ + XO;" ";NumRows * SQ + YO
   #gr "color white"
   for i = 0 to NumCols 'grid
       #gr "line ";SQ * i + XO;" ";YO;" ";SQ * i + XO;" ";YO + NumRows * SQ
   next
   for i = 0 to NumRows
       #gr "line ";XO;" ";SQ * i + YO;" ";XO + NumCols * SQ;" ";SQ * i + YO
   next
   for r = NRM1 to 0 STEP -1 'plays
       for c = 0 to NCM1
           if Grid(c, r) = P then
               #gr "color ";Browns$
               #gr "backcolor ";Browns$
           else
               if Grid(c, r) = AI then
                   if c = AIX and r = AIY then 'highlite last AI move
                       #gr "color ";104;" ";0;" ";68
                       #gr "backcolor ";104;" ";0;" ";68
                   else
                       #gr "color ";Ravens$
                       #gr "backcolor ";Ravens$
                   end if
               end if
           end if
           if Grid(c, r) then
               #gr "place ";c * SQ + XO + 3;" ";r * SQ + YO + 3
               #gr "boxfilled ";c * SQ + XO + 3 + SQ - 6;" ";r * SQ + YO + 3 + SQ - 6
           end if
           s$ = Str$(Scores(c))
           #gr "color white"
           #gr "backcolor black"
           call Text XO + c * SQ + (60 - LEN(s$) * 7) / 2, YO + SQ * NumRows + 38, str$(Scores(c))
       next
   next
   check = CheckWin()
   if check then 'report end of round and see if want to play again
       if check = 4 or check = -4 then
           #gr "color white"
           for i = 0 to 3
               #gr "place ";(WinX + i * DX(WinD)) * SQ + XO + 5;" ";(WinY + i * DY(WinD)) * SQ + YO + 5
               #gr "box ";(WinX + i * DX(WinD)) * SQ + XO + 5 + SQ - 10;" ";(WinY + i * DY(WinD)) * SQ + YO + 5 + SQ - 10
           next
       end if
       for r = 0 to NRM1
           for c = 0 to NCM1
               if Record$(c, r) <> "" then
                   s$ = mid$(Record$(c, r), 1, instr(Record$(c, r), " ") - 1)
                   if right$(Record$(c, r), 1) = "A" then
                       #gr "backcolor ";Ravens$
                   else
                       #gr "backcolor ";Browns$
                   end if
                   call Text SQ * c + XO + (SQ - LEN(s$) * 7) / 2, SQ * r + YO + 38, s$
               end if
           next
       next
       if check = -4 then
           s$ = "AI is Winner!"
       else
           if check = 4 then
               s$ = "Human is Winner!"
           else
               if check = N then
                   s$ = "Board is full, no winner." ' keep Turn the same
               end if
           end if
       end if
       #gr "color white"
       #gr "backcolor black"
       call CText 32, s$
       Kee$ = ""
       call CText 64, "Play again? just press spacebar, quit with any other."
       while len(Kee$) = 0 : scan : wend
       if Kee$ = " " then
           dim Grid(NCM1, NRM1)
           if GoFirst = P then GoFirst = AI else GoFirst = P
           Turn = GoFirst: MoveNum = 0
       else
          GameOn = 0
          notice "Goodbye!"
       end if
   end if
end sub

sub Text x, y, message$ 'note: have to reset fore or back color after ink
   #gr "place ";x;" ";y;";|";message$
end sub

sub CText y, message$ ' center text on lower left? y pixel
   call Text (SW - len(message$) * 7) / 2, y, message$
end sub

sub LButtonUp H$, mx, my  'must have handle and mouse x,y
   MouseX = mx : MouseY = my
end sub

sub CharIn H$, c$
   Kee$ = c$
end sub

sub Quit H$
   close #gr
   end
end sub

sub Pause mil   'tsh version has scan built-in
   t0 = time$("ms")
   while time$("ms") < t0 + mil : scan : wend
end sub


Yes, there is still hope for Human players

[tsh73]

fixed major flicker on my netbook by moving ShowGrid
[/b]            MouseX = -1 : MouseY = -1
       call ShowGrid
       end if
   else
       call AIMove
        Turn = P: MoveNum = MoveNum + 1
       call ShowGrid
   end if
   call Pause 200
wend

Summary (resume) by me and my 10-year child:
AI is definitely evil and impossible to beat! $)