100 REM BASIC Week 3: Under the Sea
 110 REM http://reddit.com/r/RetroBattlestations
 120 REM written by FozzTexx
 130 REM IBM PC version by FozzTexx

 200 REM Clear screen and setup variables
 210 CLS
 220 COLS = 80:ROWS = 24:REM Columns and Rows of screen
 230 GOSUB 2010:Turtle$ = SP$:TurtleWidth = SC:TurtleHeight = SR
 240 TurtleErase$ = SE$:GOSUB 2010:TurtleDead$ = SP$
 250 FOR EE = 1 TO 3:GOSUB 2010:Enemy$(EE) = SP$
 260 EnemyErase$(EE) = SE$:EnemyW(EE) = SC:NEXT EE
 270 GOSUB 2010:GameOver$ = SP$:GOWidth = SC:GOHeight = SR
 280 AirMax = 10:Sea$ = "-_."
 290 TurtleY = 18:Surface = 4:GOSUB 4100:Score = -10:GOSUB 4510

 300 REM Play game
 310 X = 1:Y = Surface:GOSUB 1010
 320 FOR I = 1 TO COLS:PRINT MID$(Sea$, INT(RND * 3) + 1, 1);:NEXT I
 330 GOSUB 5140:GOSUB 6660:GOSUB 6140
 340 LastY = TurtleY
 350 FOR TurtleX = 1 TO COLS
 360 IF LastY <> TurtleY THEN GOSUB 3510
 370 GOSUB 5010:GOSUB 6510:GOSUB 6010
 380 SP$ = Turtle$:X = TurtleX:Y = TurtleY:GOSUB 1510
 390 LastY = TurtleY:GOSUB 2510
 400 IF KE$ = "A" OR KE$ = "a" THEN D = -1:GOSUB 3010
 410 IF KE$ = "Z" OR KE$ = "z" THEN D = 1: GOSUB 3010
 420 IF KE$ = "Q" OR KE$ = "q" THEN END
 430 IF TurtleY = Surface + 1 THEN GOTO 450
 440 IF TurtleX = (COLS / 4) OR TurtleX = (COLS / 4) * 3 THEN GOSUB 4010
 450 IF TurtleY = Surface + 1 AND Air < AirMax THEN GOSUB 4100
 460 NEXT TurtleX
 470 GOTO 310
 
1000 REM Position cursor at X,Y
1010 LOCATE Y,X
1020 RETURN

1500 REM Draw sprite in SP$ at X,Y
1510 SE = 1:SB = 1
1520 IF X < 1 OR X > COLS OR Y < 1 OR Y > ROWS THEN RETURN
1530 SE = INSTR(SB, SP$, CHR$(13))
1540 IF SE = 0 THEN SE = LEN(SP$) + 1
1550 GOSUB 1010
1560 SL = SE - SB:IF SL + X - 1 > COLS THEN SL = COLS - X + 1
1570 PRINT MID$(SP$, SB, SL);
1580 IF SE >= LEN(SP$) THEN RETURN
1590 IF ASC(MID$(SP$, SE)) = 13 THEN SE = SE +  1
1600 SB = SE:Y = Y + 1:GOTO 1520

2000 REM Load a sprite from DATA into SP$
2010 SP$ = "":SE$ = "":SR = 0:SC = 0
2020 READ T$,S$:IF LEN(SP$) > 0 THEN SP$ = SP$ + CHR$(13)
2030 SP$ = SP$ + S$:SR = SR + 1:IF LEN(S$) > SC THEN SC = LEN(S$)
2040 BL$ = "":FOR I = 1 TO LEN(S$):BL$ = BL$ + " ":NEXT I
2050 IF LEN(SE$) > 0 THEN SE$ = SE$ + CHR$(13)
2060 SE$ = SE$ + BL$
2070 IF T$ <> "SE" THEN GOTO 2020
2080 RETURN

2500 REM Read the keyboard
2510 KE$ = INKEY$
2520 RETURN

3000 REM Player wants to move turtle up or down
3010 TurtleY = TurtleY + D
3020 IF TurtleY <= Surface THEN TurtleY = Surface + 1
3030 IF TurtleY > ROWS - TurtleHeight + 1 THEN TurtleY = ROWS - TurtleHeight + 1
3040 RETURN

3500 REM Turtle moved up or down, erase from previous line
3510 Y = LastY:IF LastY > TurtleY THEN Y = Y + TurtleHeight - 1
3520 X = TurtleX:SP$ = TurtleErase$:GOSUB 1510
3530 RETURN

4000 REM Show remaining air
4010 Air = Air - 1:IF Air < 0 THEN Air = 0
4020 IF Air > AirMax THEN Air = AirMax
4030 X = COLS - 7 - AirMax:Y = 2:GOSUB 1010
4040 PRINT "Air: |";
4050 FOR I = 1 TO Air:PRINT "#";:NEXT I
4060 IF Air < AirMax THEN FOR I = Air + 1 TO AirMax:PRINT " ";:NEXT I
4070 PRINT "|";
4080 IF Air = 0 THEN GOTO 4110
4090 RETURN
4100 Air = AirMax:GOTO 4030
4110 FOR I = TurtleY to Surface + 1 STEP -1
4120 X = TurtleX:Y = I:SP$ = TurtleDead$:GOSUB 1510
4130 Y = Y + 1:SP$ = TurtleErase$:GOSUB 1510
4140 NEXT I
4150 X = (COLS - GOWidth) / 2:Y = (ROWS - GOHeight) / 2
4160 SP$ = GameOver$:GOSUB 1510
4170 X = 1:Y = ROWS - 2:GOSUB 1010
4180 END

4500 REM Display score
4510 Score = Score + 10:OX = X:OY = Y
4520 X = 2:Y = 2:GOSUB 1010:PRINT "Score: ";Score;
4540 X = OX:Y = OY:RETURN

5000 REM Take care of bubbles
5010 FOR BB = 1 to NumBubbles
5020 IF INT(BubbleY(BB)) <= Surface THEN GOTO 5120
5030 NewY = BubbleY(BB) - (ROWS / COLS)
5040 X = BubbleX(BB):Y = INT(BubbleY(BB))
5050 GOSUB 5510:IF Hit = 0 THEN GOTO 5080
5060 Air = Air + 2:IF Bubble$(BB) = "O" THEN AIR = AIR + 1
5070 GOSUB 4010:NewY = ROWS + COLS
5080 IF INT(NewY) = Y THEN GOTO 5110
5090 SP$ = " ":GOSUB 1510:SP$ = Bubble$(BB):Y = INT(NewY)
5100 IF Y > Surface THEN GOSUB 1510
5110 BubbleY(BB) = NewY
5120 NEXT BB
5130 RETURN
5140 NumBubbles = INT(RND * 3) + 1:FOR BB = 1 to NumBubbles
5150 BubbleX(BB) = INT(RND * COLS) + 1:BubbleY(BB) = ROWS - INT(RND * 3)
5160 Bubble$(BB) = CHR$(79 + INT(RND * 2) * 32)
5170 NEXT BB:RETURN

5500 REM Hit detection
5510 Hit = 0
5520 IF X < TurtleX + TurtleWidth - 2 THEN RETURN
5530 IF X > TurtleX + TurtleWidth + 1 THEN RETURN
5540 IF Y < TurtleY - 1 THEN RETURN
5550 IF Y > TurtleY + 1 THEN RETURN
5560 Hit = 1:RETURN

6000 REM Take care of enemies
6010 FOR EE = 1 to NumEnemies
6020 IF INT(EnemyY(EE)) <= Surface THEN GOTO 6120
6030 NewX = EnemyX(EE) + EnemyXV(EE):NewY = EnemyY(EE) + EnemyYV(EE)
6040 X = INT(EnemyX(EE)):Y = INT(EnemyY(EE))
6050 IF EnemyHit(EE) = 1 THEN GOTO 6070
6060 GOSUB 5510:IF Hit = 1 THEN GOSUB 4010:EnemyHit(EE) = 1
6070 IF INT(NewX) = X AND INT(NewY) = Y THEN GOTO 6110
6080 SP$ = EnemyErase$(EnemyC(EE)):GOSUB 1510
6090 SP$ = Enemy$(EnemyC(EE)):X = INT(NewX):Y = INT(NewY)
6100 IF Y > Surface THEN GOSUB 1510
6110 EnemyX(EE) = NewX:EnemyY(EE) = NewY
6120 NEXT EE
6130 RETURN
6140 FOR EE = 1 TO NumEnemies:SP$ = EnemyErase$(EnemyC(EE))
6150 X = INT(EnemyX(EE)):Y = INT(EnemyY(EE)):GOSUB 1510:NEXT EE
6160 NumEnemies = INT(RND * 3) + 1:FOR EE = 1 to NumEnemies
6170 EnemyX(EE)=INT(RND*COLS)+1:EnemyY(EE)=ROWS-INT(RND*(ROWS - Surface))
6180 EnemyXV(EE) = RND:EnemyYV(EE) = RND * ((ROWS - Surface) / COLS)
6190 EnemyC(EE) = INT(RND * 3) + 1:EnemyHit(EE) = 0
6200 IF EnemyX(EE) > COLS / 2 THEN EnemyXV(EE) = - EnemyXV(EE)
6210 IF EnemyY(EE) > ROWS / 2 THEN EnemyYV(EE) = - EnemyYV(EE)
6220 NEXT EE:RETURN

6500 REM Take care of food
6510 FOR FF = 1 to NumFood
6520 X = FoodX(FF):Y = INT(FoodY(FF)):GOSUB 5510
6530 IF Hit = 1 THEN GOSUB 4510:SP$ = " ":GOSUB 1510:FoodY(FF) = ROWS + COLS
6640 NEXT FF
6650 RETURN
6660 SP$=" ":FOR FF=1 TO NumFood:X = FoodX(FF):Y = FoodY(FF):GOSUB 1510:NEXT FF
6670 NumFood = INT(RND * 3) + 1:FOR FF = 1 to NumFood
6680 FoodX(FF)=INT(RND * COLS) + 1:FoodY(FF)=ROWS - INT(RND * (ROWS - Surface))
6690 Food$(FF) = CHR$(120 + INT(RND * 2))
6700 X = FoodX(FF):Y = FoodY(FF):SP$ = Food$(FF):GOSUB 1510
6710 NEXT FF:RETURN

9000 DATA SP," _-%#%#}o"
9010 DATA SE,"       )"
9020 DATA SE,"  -OOOO}x"
9030 DATA SE,"^;;^"
9040 DATA SE,"<><"
9050 DATA SE,"$"
9060 DATA SP," _   _          __      _       __  _"
9070 DATA SP,"/ \ / \ |\  /| |       / \ | | |   | \"
9080 DATA SP,"| _ |_| | \/ | |--  *  | | \ / |-- |_/"
9090 DATA SE,"\_/ | | |    | |__     \_/  V  |__ | \"