1.1 --- a/mapcode.oph	Thu Aug 25 01:41:46 2011 +0200
     1.2 +++ b/mapcode.oph	Thu Aug 25 01:42:30 2011 +0200
     1.3 @@ -2959,6 +2959,43 @@
     1.4      clc
     1.5      rts
     1.6  
     1.7 +; The player collision masks use bits to represent where the player is in a
     1.8 +; tile.
     1.9 +
    1.10 +; Player is above, enemy is below, checking the overlap in the lower tile.
    1.11 +player_collision_mask_above: .byte $00, $20, $30, $38, $3c, $3e
    1.12 +
    1.13 +projectile_collision_mask_above: .byte $00, $00, $00, $00, $00, $20
    1.14 +
    1.15 +; Player and enemy share the same tile or player is on the tile below.
    1.16 +player_collision_mask_below:  .byte $3f, $1f, $0f, $07, $03, $01
    1.17 +
    1.18 +projectile_collision_mask_below: .byte $30, $18, $0c, $06, $03, $01
    1.19 +
    1.20 +; Player is above or on the same tile, enemy is below, checking the overlap in
    1.21 +; the lower tile.
    1.22 +enemy_collision_mask_above:  .byte $3c, $1e, $0f, $07, $03, $01
    1.23 +
    1.24 +; Enemy is above, player is below, checking the overlap in the lower tile.
    1.25 +enemy_collision_mask_below: .byte $00, $00, $00, $20, $30, $38
    1.26 +
    1.27 +; Player is to the left, enemy is to the right, checking the overlap in the
    1.28 +; right hand tile.
    1.29 +player_collision_mask_left:
    1.30 +projectile_collision_mask_left: .byte $00, $00, $00, $08
    1.31 +
    1.32 +; Player and enemy share the same tile or player is on the tile to the right.
    1.33 +player_collision_mask_right:
    1.34 +projectile_collision_mask_right: .byte $0c, $06, $03, $01
    1.35 +
    1.36 +; Player is to the left, enemy is to the right or on the same tile, checking
    1.37 +; the overlap in the right hand tile.
    1.38 +enemy_collision_mask_left:  .byte $0f, $07, $03, $01
    1.39 +
    1.40 +; Enemy is to the left, player is to the right, checking the overlap in the
    1.41 +; right hand tile.
    1.42 +enemy_collision_mask_right: .byte $00, $08, $0c, $0e
    1.43 +
    1.44  player_collide:
    1.45  
    1.46      lda #$0c            ; set the character address
    1.47 @@ -2990,37 +3027,47 @@
    1.48          jmp player_collide_next
    1.49  
    1.50          player_check_collide_y_equal:
    1.51 +        ; The enemy is on the same tile as the player so look at the collision
    1.52 +        ; on their common tile.
    1.53 +        ldx $3303                           ; player dy
    1.54 +        lda player_collision_mask_below,x
    1.55 +        sta $80
    1.56          ldy #3
    1.57 -        lda ($74),y         ; dy
    1.58 -        sec
    1.59 -        sbc $3303           ; dy - player dy    ; this appears to be
    1.60 -        bmi player_check_collide_y_equal_n      ; required to deal with
    1.61 -                                                ; negative results
    1.62 -
    1.63 -        jmp player_check_collide_x
    1.64 -
    1.65 -        player_check_collide_y_equal_n:         ; dy - dpy <= -4 (to miss)
    1.66 -        cmp #253                                ; dy - dpy > -3 (to hit)
    1.67 -        bpl player_check_collide_x
    1.68 +        lda ($74),y                         ; dy
    1.69 +        tax
    1.70 +        lda enemy_collision_mask_above,x
    1.71 +        and $80
    1.72 +        bne player_check_collide_x
    1.73  
    1.74          jmp player_collide_next
    1.75  
    1.76 -        player_check_collide_y_greater:         ; DY - dpy >= 6 (to miss)
    1.77 -        ldy #3                                  ; DY = 6 + dy  (coordinates)
    1.78 -        lda ($74),y         ; dy                ; 6 + dy - dpy >= 6
    1.79 -        sec                                     ; dy - py >= 0
    1.80 -        sbc $3303           ; dy - player dy    ; dy - py < 0 (to hit)
    1.81 -        bmi player_check_collide_x
    1.82 +        player_check_collide_y_greater:
    1.83 +        ; The enemy is on the tile below the player so look at the collision on
    1.84 +        ; the enemy's tile.
    1.85 +        ldx $3303                           ; player dy
    1.86 +        lda player_collision_mask_above,x
    1.87 +        sta $80
    1.88 +        ldy #3
    1.89 +        lda ($74),y                         ; dy
    1.90 +        tax
    1.91 +        lda enemy_collision_mask_above,x
    1.92 +        and $80
    1.93 +        bne player_check_collide_x
    1.94  
    1.95          jmp player_collide_next
    1.96  
    1.97 -        player_check_collide_y_less:            ; DPY - dy >= 4 (to miss)
    1.98 -        ldy #3                                  ; DPY = 6 + dpy
    1.99 -        lda ($74),y         ; dy                ; 6 + dpy - dy >= 4
   1.100 -        sec                                     ; dy - dpy <= 2
   1.101 -        sbc $3303           ; dy - player dy
   1.102 -        cmp #3
   1.103 -        bpl player_check_collide_x
   1.104 +        player_check_collide_y_less:
   1.105 +        ; The enemy is on the tile above the player so look at the collision on
   1.106 +        ; the player's tile.
   1.107 +        ldx $3303                           ; player dy
   1.108 +        lda player_collision_mask_below,x
   1.109 +        sta $80
   1.110 +        ldy #3
   1.111 +        lda ($74),y                         ; dy
   1.112 +        tax
   1.113 +        lda enemy_collision_mask_below,x
   1.114 +        and $80
   1.115 +        bne player_check_collide_x
   1.116  
   1.117          jmp player_collide_next
   1.118  
   1.119 @@ -3038,32 +3085,47 @@
   1.120          jmp player_collide_next
   1.121  
   1.122          player_check_collide_x_equal:
   1.123 +        ; The enemy is on the same tile as the player so look at the collision
   1.124 +        ; on their common tile.
   1.125 +        ldx $3305                           ; player dx
   1.126 +        lda player_collision_mask_right,x
   1.127 +        sta $80
   1.128          ldy #5
   1.129 -        lda ($74),y         ; dx
   1.130 -        sec
   1.131 -        sbc $3305           ; dx - player dx
   1.132 -        cmp #2                                  ; dx - dpx >= 2 (to miss)
   1.133 -        bpl player_collide_next                 ; dx - dpx < 2 (to hit)
   1.134 -        jmp player_check_collide_destroy
   1.135 +        lda ($74),y                         ; dx
   1.136 +        tax
   1.137 +        lda enemy_collision_mask_left,x
   1.138 +        and $80
   1.139 +        bne player_check_collide_destroy
   1.140 +
   1.141 +        jmp player_collide_next
   1.142  
   1.143          player_check_collide_x_greater:
   1.144 +        ; The enemy is the tile to the right of the player so look at the
   1.145 +        ; collision on the enemy's tile.
   1.146 +        ldx $3305                           ; player dx
   1.147 +        lda player_collision_mask_left,x
   1.148 +        sta $80
   1.149          ldy #5
   1.150 -        lda $3305           ; player dx
   1.151 -        sec
   1.152 -        sbc ($74),y         ; player dx - dx
   1.153 -        cmp #3                                  ; dpx - dx > 2 (to hit)
   1.154 -        bpl player_check_collide_destroy
   1.155 +        lda ($74),y                         ; dx
   1.156 +        tax
   1.157 +        lda enemy_collision_mask_left,x
   1.158 +        and $80
   1.159 +        bne player_check_collide_destroy
   1.160  
   1.161          jmp player_collide_next
   1.162  
   1.163 -        player_check_collide_x_less:            ; PX - x >= 4 (to miss)
   1.164 -        ldy #5                                  ; PX = 4 + px
   1.165 -        lda ($74),y         ; dx                ; 4 + px - x >= 4
   1.166 -        sec                                     ; x - px <= 0
   1.167 -        sbc $3305           ; dx - player dx
   1.168 -        bmi player_collide_next
   1.169 -        cmp #1                                  ; x - px >= 1 (to hit)
   1.170 -        bpl player_check_collide_destroy
   1.171 +        player_check_collide_x_less:
   1.172 +        ; The enemy is the tile to the left of the player so look at the
   1.173 +        ; collision on the player's tile.
   1.174 +        ldx $3305                           ; player dx
   1.175 +        lda player_collision_mask_right,x
   1.176 +        sta $80
   1.177 +        ldy #5
   1.178 +        lda ($74),y                         ; dx
   1.179 +        tax
   1.180 +        lda enemy_collision_mask_right,x
   1.181 +        and $80
   1.182 +        bne player_check_collide_destroy
   1.183  
   1.184          player_collide_next:
   1.185          clc