PETSCII Raiders (C64) by Peter Caspari

Petscii Raiders

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Written by Peter Caspari for the BASIC 10Liner Contest 2023.

Language: Commodore 64 Basic v2

Category: PUR-120

The game

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Based on the classic space invaders game.  Destroy all raiders while avoiding guided projectiles from the mother ship at the top of the screen

Controls and play

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Use left, right and fire on the joystick in port 2.

Expanded and commented version.  Can be cut and pasted directly into CBM prg Studio

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0 dims$(42):N=54272:V=53248:X=99:reada$,p$,d$:rem setup variables

1B$="{down*2}"+A$+A$+A$+A$+"{down}":rem setup raider string

2I$="{148} {down}{left}":J$=" "+CHR$(20)+"{down}":FORT=1TO23:L$=L$+I$

10 M$=M$+J$:NEXT:rem create strings to shift raiders left and right

11PRINT"{clear}";:POKEV+1,229:POKEv+5,99:rem sprite initial locations

12POKE2040,13:POKE2041,14:POKE2042,15:rem setup sprite memory locations

13SYS59749:rem initiate vertical scrolling call

14POKE210,208:PRINTTAB(21)p$:rem setup sprite with print to memory hack

15POKE995,7:POKE998,7:rem rem draw bomb sprite

20 FORT=832TO892STEP3:POKET+1,ASC(MID$(d$,(T-832)/3+1,1)):POKET+66,1:rem draw ship and laser sprite

21d=d+1:s$(d)=L$:s$(d+21)=M$:NEXT:rem create strings to shift raiders left and right

22 POKEN+24,15:POKEN+5,9:rem setup sound

30 POKEN+6,63:POKEV+30,0:POKEN+4,33:pokev+30,0:rem setup sound

31 h=0:c=0:e=40:b=165:l=l+1:rem initial variable settings

32 PRINT"{home}{yellow}"b$:?"{green}"b$:ifl>1then?"{purple}"b$:ifl>2then?"{cyan}"b$:rem setup screen

40 PRINT"{home}{light green}hits"S"{left}  {blue}level"l"{left}  {red}{cm q}{reverse on}--{reverse off}{cm w}":PRINT"{home}{down}";:rem draw header

41C=C+1:?s$(c)"{home}":IFC=21orc=42THENSYS59777:B=165:e=40:rem scroll raiders and reset bomb

50 b=b+sgn(x-b)*(l+1):e=e+12:e=abs(255-e):e=255-e:rem move bomb

51J=PEEK(56320):X=abs(X+6*(SGN(JAND4)-SGN(JAND8))):x=abs(255-x):x=255-x:rem move ship

52 ifc=42thenc=0:rem reset scrolling

60 pokev+4,b:pokev+5,e:i=0:rem render bomb

61 POKEV,X:POKEV+2,X:rem set x position for ship and laser

62 if(JAND16)=16thenforz=1to150:next:rem delay when not firing

63 goto90:data "{space}{cm b} {reverse on}{cm b}{reverse off}{space}{down}{left*5} {reverse on}W.W{reverse off}{space}{down}{left*5}{space}{reverse on}{cm b}{cm t}{reverse off}{cm b}{space}{up*2}{left}"

69 rem fire laser and exit when collision detected

70 pokev+2,x:forj=208to80step-8:pokev+3,j:POKEN+1,j:if(PEEK(V+31)AND2)=0thennext:goto90:data"7{right}0{right*3}0{right}1{right}000{right*5}311"

80 FP=1024+(X)/8+INT((J-42)/8)*40:rem convert sprite location to screen memory location

81 i=sgn(peek(fp)-32)+sgn(peek(fp-40)-32):rem count sparts of raider hit

82 h=h+i:rem hit counter

83 POKEFP,32:pokeFP-40,32:rem clear hit parts of raider

84 ifh=32+l*32orh=128then30:rem check if level completed

90 s=s+i:rem increment score

91 POKEN+1,20:pokev+3,0:POKEN+1,0:rem beep and clear laser

92 ifPEEK(V+31)<>1and(PEEK(V+30)AND1)=0then40:rem check for collisions

93 data"zzzzzzz{cm x}{cm x}{cm x}{pi}{pi}{cm x}{cm x}{cm x}{cm x}{cm x}{pi}{pi}{cm x}{cm x}"