*=$0801 ; 2018 SYS 2062 !word main-2, 10 !byte $9e !text " 2062" !byte $00,$00,$00 !set MAXSPRITES = $20 !set INDEX = $20 ;$CD00 !set XPOS = $40 ; $CD80 !set YPOS = $60 ; $CE00 !set XMSB = $80 ; $CE80 !set COLOR = $a0 ; $CF00 !set POINTER = $c0 ; $CF80 !set SPRITECOUNT =$fb ; Number of sprites !set CURRENTSPRITE =$fc ;Current sprite !set SWAPPED = $fd ; For sort ;Zero page bit masks !set ANDBITS =$e0 !set ANDBITS_NEG =$e8 !set RASTERSETUP = 0 !set DEBUG = 1 ;Based on SQUARE DEMO disassembly. All logic intact. ;Did find some optimizations. Take that, 17-year old me! ;Pre-calculating the shifted sine table would save time main ;clear screen LDA #147 JSR $FFD2 SEI LDA #%01111111 ; switch off interrupt signals from CIA-1 STA $DC0D AND $D011 ; clear most significant bit of VIC's raster register STA $D011 LDA $DC0D ; acknowledge pending interrupts from CIA-1 LDA $DD0D ; acknowledge pending interrupts from CIA-2 ;sprite data LDX #63 SPRD LDA SPRIBITS,X STA $3FC0,X DEX BPL SPRD ;set up bit masks LDX #7 LDA #128 NB STA ANDBITS,X PHA EOR #$FF STA ANDBITS_NEG,X PLA CLC ROR DEX BPL NB JSR SETUPMP JSR TESTSPRITESSIN JSR SORT LDA #TOPRASTER STA $0315 LDA #RASTERSETUP STA $D012 LDA #1 STA $D01A CLI LDA #0 WAIT BEQ WAIT TOPRASTER LDA $D019 STA $D019 !IFDEF DEBUG{ LDA #8 STA $D020 } JSR UPDATESIN !IFDEF DEBUG{ LDA #2 STA $D020 } JSR SORT !IFDEF DEBUG{ LDA #0 STA $D020 } LDA #0 STA $D010 ;We assume at least 8 sprites LDA #255 STA $D015 ; Setup first sprites LDY #$00 LC09E LDX INDEX,Y LDA COLOR,X STA $D027,Y LDA POINTER,X STA $07F8,Y LDA XMSB,X BEQ LC0C4 LDA $d010 ORA ANDBITS,Y STA $d010 LC0C4 TYA ASL TAY LDA XPOS ,X STA $D000,Y LDA YPOS,X STA $D001,Y TYA LSR TAY INY CPY SPRITECOUNT BEQ LC105 CPY #$08 BNE LC09E STY CURRENTSPRITE ;Set up interrupt CLC LDX INDEX LDA YPOS,X ADC #$15 ;LC0EC CMP #$F8 ;LC0EE BCS LC105 ; Check if sprite is below border, never mind STA $D012 LDA #nextsprite STA $0315 LC105 ; no more sprites !ifdef DEBUG{ LDA #14 STA $D020 } JMP $EA81 ;Individual sprite setup nextsprite !ifdef DEBUG{ INC $D020 } LDA $D019 STA $D019 LDY CURRENTSPRITE ;Current sprite to show NSLOOP LDX INDEX,Y TYA AND #$07 ;Mask to find relevant hardware sprite TAY LDA POINTER,X ;Sprite pointer STA $07F8,Y LDA COLOR,X ;Sprite color STA $D027,Y LDA XMSB,X ;Sprite X high bit BEQ NSNOH LDA $D010 ORA ANDBITS,Y ;Set X high bit BNE NSNOH2 NSNOH LDA $D010 AND ANDBITS_NEG,Y ;Clear X high bit NSNOH2 STA $D010 TYA ASL TAY LDA YPOS,X ;Y position STA $D001,Y LDA XPOS,X ;X Position STA $D000,Y INC CURRENTSPRITE ;Go to next sprite LDY CURRENTSPRITE CPY SPRITECOUNT BEQ NOMORESPRITES ;Stop if we are the end of the sprite list LDX INDEX-8,y ;Look at the topmost sprite currently being displayed LDA YPOS,x ADC #$15 ;Line at end of that sprite CMP $D012 ; Is this the line we are already on or passed, then do it right away BEQ NSLOOP BCC NSLOOP STA $D012 ;If not, set next raster interrupt line !ifdef DEBUG{ DEC $D020 } JMP $EA81 NOMORESPRITES LDA #TOPRASTER STA $0315 LDA #RASTERSETUP STA $D012 !ifdef DEBUG{ DEC $D020 } JMP $EA81 TESTSPRITESSIN LDX #0 TSS1 LDA #255 STA POINTER,X LDA COLORS,X STA COLOR,X INX CPX #32 BNE TSS1 STX SPRITECOUNT JSR UPDATESIN RTS UPDATESIN INC SINPOS LDX #0 LDY SINPOS USP1 LDA COSTABLE,Y CLC ADC #35 STA XPOS,X LDA #0 ROL STA XMSB,X LDA SINTABLE,Y STA YPOS,X TYA ;clc ; Not necessary, as xpos is never > 256+128 and ROL therefore never sets carry ADC #8 ; JUMP 8 POSITIONS TAY INX CPX SPRITECOUNT BNE USP1 RTS SETUPMP LDX #$00 LC009 LDA #$00 STA XPOS,X STA XMSB,X STA COLOR,X STA POINTER,X LDA #$FF STA YPOS,X TXA STA INDEX,X INX CPX #MAXSPRITES BNE LC009 RTS SORT ;why make it more complicated? ;mostly marginally faster than regular bubble sort, worst case is better LDX #$01 LC073 LDY INDEX,X LDA YPOS,Y LDY INDEX-1,X CMP YPOS,Y BCS LC096 LDA INDEX,X STA INDEX-1,X TYA STA INDEX,X ;If we have swapped and are >0 move back to see if it needs to go further up DEX BNE LC073 INX LC096 INX CPX SPRITECOUNT BNE LC073 RTS SPRIBITS !byte 0,127,0,1,255,192,3,255,224,3,231,224 !byte 7,217,240,7,223,240,7,217,240,3,231,224 !byte 3,255,224,3,255,224,2,255,160,1,127,64 !byte 1,62,64,0,156,128,0,156,128,0,73,0,0,73,0 !byte 0,62,0,0,62,0,0,62,0,0,28,0 SINPOS !byte 0 COSTABLE !fill 256, [137 + 110 * math.sin( i * 360 / 256 )] SINTABLE !fill 256, [137 +80 * math.cos( i * 360 / 256 )] COLORS !byte 0,1,2,3,4,5,7,8,9,10,11,12,13,14,15,0,1,2,3,4,5,7,8,9,10,11,12,13,14,15,1,2,3,4