diff options
| author | Jesse Luehrs <doy@tozt.net> | 2014-10-09 19:24:54 -0400 |
|---|---|---|
| committer | Jesse Luehrs <doy@tozt.net> | 2014-10-09 19:27:48 -0400 |
| commit | fecc4a9f341cc21690278f6aab07c4cdc3bb3311 (patch) | |
| tree | 20ed50d135a551144950368f5291b043f71186bb | |
| parent | bfa5d4aeeb976ebf7718e27cd4d82f930cbdbece (diff) | |
| download | nes-snake-fecc4a9f341cc21690278f6aab07c4cdc3bb3311.tar.gz nes-snake-fecc4a9f341cc21690278f6aab07c4cdc3bb3311.zip | |
also erase old sprites from the tail
this breaks startup somehow, but only sometimes
| -rw-r--r-- | main.s | 123 |
1 files changed, 72 insertions, 51 deletions
@@ -84,13 +84,14 @@ clrmem: LDA #$00 STA $0000, x STA $0100, x - STA $0300, x - STA $0400, x STA $0500, x STA $0600, x STA $0700, x LDA #$FE STA $0200, x + LDA #$80 + STA $0300, x + STA $0400, x INX BNE clrmem @@ -158,51 +159,20 @@ reset_sprites_jmp: JMP reset_sprites draw_game: - LDA #$20 - STA vram_addr_high - LDA #$E0 - STA vram_addr_low - - LDY #$01 - LDA (head), y - SEC - SBC #$35 - LSR - LSR - LSR - TAX -- CLC - LDA vram_addr_low - ADC #$20 - STA vram_addr_low - LDA vram_addr_high - ADC #$00 - STA vram_addr_high - DEX - BNE - - - LDY #$00 - LDA (head), y + LDX #$00 + JSR draw_sprite_at_head + LDA head SEC - SBC #$40 - LSR - LSR - LSR + SBC length + SBC length + STA head + LDX #$20 + JSR draw_sprite_at_head CLC - ADC #$08 - ADC vram_addr_low - STA vram_addr_low - LDA vram_addr_high - ADC #$00 - STA vram_addr_high - - LDA vram_addr_high - STA $2006 - LDA vram_addr_low - STA $2006 - - LDA #$00 - STA $2007 + LDA head + ADC length + ADC length + STA head LDA #$20 STA $2006 @@ -210,21 +180,19 @@ draw_game: STA $2006 LDA apple.y - STA $0204 + STA $0200 LDA #$07 - STA $0205 + STA $0201 LDA #$00 - STA $0206 + STA $0202 LDA apple.x - STA $0207 + STA $0203 JMP do_dmi reset_sprites: LDA #$FE STA $0200 STA $0203 - STA $0204 - STA $0207 do_dmi: LDA #$00 @@ -411,6 +379,11 @@ start_game: ; {{{ LDY #$01 STA (head), y + LDA #$01 + STA length + LDA #$00 + STA direction + JSR new_apple - BIT $2002 @@ -537,6 +510,54 @@ new_apple: ; {{{ ADC #$3D STA apple.y RTS ; }}} +draw_sprite_at_head: ; {{{ + LDA #$20 + STA vram_addr_high + LDA #$E0 + STA vram_addr_low + + LDY #$01 + LDA (head), y + SEC + SBC #$35 + LSR + LSR + LSR + TAY +- CLC + LDA vram_addr_low + ADC #$20 + STA vram_addr_low + LDA vram_addr_high + ADC #$00 + STA vram_addr_high + DEY + BNE - + + LDY #$00 + LDA (head), y + SEC + SBC #$40 + LSR + LSR + LSR + CLC + ADC #$08 + ADC vram_addr_low + STA vram_addr_low + LDA vram_addr_high + ADC #$00 + STA vram_addr_high + + LDA vram_addr_high + STA $2006 + LDA vram_addr_low + STA $2006 + + TXA + STA $2007 + + RTS ; }}} rand4: ; {{{ JSR rand1 LDX rand_out |