10 REM BASIC Week 3: Under the Sea
 20 REM http://reddit.com/r/RetroBattlestations
 30 REM Written by FozzTexx
 40 REM BBC Basic version by lolbar
 
 100 MODE 4
 110 VDU 4
 120 VDU 12
 130 VDU 23,1,0;0;0;0: REM CURSOR OFF
 
 150 REM CLEAR SCREEN AND SETUP VARIABLES
 160 CLS
 170 DIM SEA$(2):
 180 DIM ENEMYW(3),ENEMYX(3),ENEMYY(3),ENEMYXV(3),ENEMYYV(3),ENEMYC(3),ENEMYHIT(3),ENEMYERASE$(3),ENEMY$(3)
 190 DIM BUBBLEX(3),BUBBLEY(3),BUBBLE$(3),FOOD$(3),FOODX(3),FOODY(3)
 200 TURTLE=1:DEAD=3:OVER=11:NUMFOOD=0:NUMENEMIES=0
 210 COLS = 38:ROWS = 30:REM COLUMNS AND ROWS OF SCREEN
 220 GOSUB 2010:TURTLE$ = SP$:TURTLEWIDTH = SC:TURTLEHEIGHT = SR
 230 TURTLEERASE$ = SE$:GOSUB 2010:TURTLEDEAD$ = SP$
 240 FOR EE = 1 TO 3:GOSUB 2010:ENEMY$(EE) = SP$
 250 ENEMYERASE$(EE) = SE$
 260 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$(SEA$, RND(3), 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 = INT(COLS / 4) OR TURTLEX = INT(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 VDU 31,X,Y
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(SP$, CHR$(13),SB)
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$(1)
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-SURFACE) / COLS)
5040 X = BUBBLEX(BB):Y = INT(BUBBLEY(BB))
5050 GOSUB 5510:IF HIT = 0 THEN GOTO 5080
5060 AIR = AIR + 2:IF BUBBLE$(BB) = "o" THEN AIR = AIR + 1
5070 GOSUB 4010:NEWY = ROWS + COLS
5080 IF INT(NEWY) = Y THEN GOTO 5110
5090 SP$ = " ":X = BUBBLEX(BB):Y = INT(BUBBLEY(BB)):GOSUB 1510:SP$ = BUBBLE$(BB):Y = INT(NEWY)
5100 IF Y > SURFACE THEN GOSUB 1510
5110 BUBBLEY(BB) = NEWY
5120 NEXT BB
5130 RETURN
5140 NUMBUBBLES = RND(3):FOR BB = 1 TO NUMBUBBLES
5150 BUBBLEX(BB) = RND(COLS):BUBBLEY(BB) = ROWS - RND(3) - 1
5160 BUBBLE$(BB) = CHR$(79 + INT(RND(1)*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))
6070 IF INT(NEWX) = X AND INT(NEWY) = Y THEN GOTO 6110
6080 SP$ = ENEMYERASE$(ENEMYC(EE)):GOSUB 1510
6085 IF ENEMYHIT(EE) = 1 THEN GOTO 6090
6086 GOSUB 5510:IF HIT = 1 THEN GOSUB 4010:ENEMYHIT(EE) = 1
6090 SP$ = 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 = RND(3):FOR EE = 1 TO NUMENEMIES
6170 ENEMYX(EE)=INT(RND(1)*COLS)+1:ENEMYY(EE)=ROWS-INT(RND(1)*(ROWS - SURFACE))
6180 ENEMYXV(EE) = RND(1):ENEMYYV(EE) = RND(1) * ((ROWS - SURFACE) / COLS)
6190 ENEMYC(EE) = INT(RND(1) * 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$ = " ":X = FOODX(FF):Y = FOODY(FF):GOSUB 1510:FOODY(FF) = ROWS + COLS
6640 NEXT FF
6650 RETURN
6660 SP$=" ":FOR FF=1 TO NUMFOOD:X = FOODX(FF):Y = FOODY(FF):GOSUB 1510:NEXT FF
6670 NUMFOOD = INT(RND(1) * 3) + 1:FOR FF = 1 TO NUMFOOD
6680 FOODX(FF)=INT(RND(1) * COLS) + 1:FOODY(FF)=ROWS - INT(RND(1) * (ROWS - SURFACE))
6690 FOOD$(FF) = CHR$(120 + INT(RND(1) * 2))
6700 X = FOODX(FF):Y = FOODY(FF):SP$ = 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  |__ | \"