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94 lines
1.4 KiB
94 lines
1.4 KiB
INCLUDE "oam.inc"
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SECTION "Collision", ROMX
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; Determines if player has hit the background
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; @return NZ = false, Z = true
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player_bg_collides::
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; c = x % 8 == 0 ? x/8 : x/8 + 1
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ld hl, PLAYER_X
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ld a, [hl]
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ld c, a
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and %111
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jr z, .skip_inc_c
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ld a, c
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add 8
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ld c, a
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.skip_inc_c:
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srl c
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srl c
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srl c
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; b = y % 8 == 0 ? y/8 : y/8 + 1
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inc hl
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ld a, [hl]
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ld b, a
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and %111
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jr z, .skip_inc_b
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ld a, b
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add 8
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ld b, a
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.skip_inc_b:
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srl b
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srl b
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srl b
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; top left
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call can_move_to
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ret nz
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; top right
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inc c
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call can_move_to
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ret nz
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; bottom left
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dec c
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inc b
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call can_move_to
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ret nz
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; bottom right
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inc c
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call can_move_to
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ret
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; Check whether the location can be moved to or not
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; @param b y-coordinate
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; @param c x-coordinate
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; @destroy a, d, e
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; @note NZ = false, Z = true
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can_move_to:
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; todo: should be aware of scx/scy
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push bc
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push hl
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; hl = bg_collision_data
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ld hl, BG_COLLISION_DATA
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ld d, [hl]
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inc hl
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ld e, [hl]
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push de
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; de = map width
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ld hl, BG_MAP_WIDTH
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ld d, 0
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ld e, [hl]
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pop hl
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; compute map index (HL + B * (BG_MAP_WIDTH + 1) + C)
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.mul_y_width:
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add hl, de
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dec b
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jr nz, .mul_y_width
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add hl, bc
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; check [hl] = 1
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ld a, [hl]
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cp 1
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pop hl
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pop bc
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ret
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