Routines
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25677: Check Bug Flower Collision
Used by the routines at UpdateLeech, UpdateMidges and UpdateSlug.
Checks whether a bug is touching the flower, using a window that is wider for a slug than it is for the midges and the leech. It also only counts when the bug is below the top of the flower.
Input
IX Bug object
Output
E 0 No collision
E 1 Collision
BugFlowerCollision 25677 LD E,0 E=0 (no collision).
25679 LD HL,24205 HL=State_Flower_Pos_X (the X position of the flower).
Calculate the horizontal distance between the flower and the bug.
25682 LD A,(HL) A=flower X position.
25683 SUB (IX+1) Subtract the bug X position.
25686 ADD A,9 Add 9 (so a bug up to 9 pixels to the right of the flower gives zero).
25688 BIT 3,(IX+0) Jump to BugFlowerCollision_Narrow if the bug is not a slug (bit 3 of the type is set for the midges and the leech).
25692 JR NZ,BugFlowerCollision_Narrow
25694 CP 36 Compare A with 36 (the width of the window for a slug).
25696 JR BugFlowerCollision_TestX Jump to BugFlowerCollision_TestX.
BugFlowerCollision_Narrow 25698 CP 28 Compare A with 28 (the width of the window for the other bugs).
BugFlowerCollision_TestX 25700 RET NC Return if the bug is too far away horizontally.
Is the bug below the top of the flower?
25701 INC HL Increment HL by one to point to the flower Y position.
25702 LD A,(HL) Halve the flower Y position.
25703 SRL A
25705 LD D,(IX+2) Halve the bug Y position into D.
25708 SRL D
25710 SUB D Subtract the halved bug Y position from the halved flower Y position.
25711 RET NC Return if the flower is not above the bug.
25712 LD E,1 E=1 (collision).
25714 RET Return.
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