Routines
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E881: Process Wall Bouncing Enemy
Per-frame handler for the wall-bouncing enemy. If the wave start delay is still counting down, advances to the next entity record without processing. Otherwise checks for player contact via Find_Colliding_Entity and triggers player death via Strip_Attributes_And_Fade if the bouncer is touching. If the bouncer is already dying, skips to the draw step. Searches the wave enemy list for a collision via Find_Colliding_Wave_Enemy; if none is found, defers to Handle_Enemy_Collision_Chain. On a hit, decrements a countdown timer; when it expires the bouncer erases itself, nudges one step toward the player, picks a new heading, and redraws.
Input
HL Entity record pointer
If the wave is still warming up, skip ahead without processing.
Process_Wall_Bouncing_Enemy E881 LD A,($C533) If the wave start delay at Wave_Start_Delay is non-zero, skip to Process_Wall_Bouncing_Enemy_Advance.
E884 AND A
E885 JP NZ,Process_Wall_Bouncing_Enemy_Advance
Check whether the player is touching the bouncer and kill them if so.
E888 INC HL Advance to the velocity pair.
E889 INC HL
E88A EXX Switch to alternate registers.
E88B CALL Find_Colliding_Entity Search for a contact slot via Find_Colliding_Entity.
E88E JP NC,Kill_Wall_Bouncing_Enemy Jump to Kill_Wall_Bouncing_Enemy if player contact is confirmed.
E891 LD HL,$C4D4 Load the player position from Player_Y_Position and test overlap via HitTestBounds8AtHL.
E894 CALL HitTestBounds8AtHL
E897 JP NC,Strip_Attributes_And_Fade Kill the player via Strip_Attributes_And_Fade if the overlap test confirmed contact.
E89A EXX Switch back and step three bytes toward the entity record start.
E89B DEC HL
E89C DEC HL
E89D DEC HL
If the bouncer is already dying, skip directly to the draw step.
E89E DEC HL If the bouncer is already dying (bit 0 of active flag), skip to Process_Wall_Bouncing_Enemy_Advance.
E89F DEC HL
E8A0 LD A,(HL)
E8A1 SRL A
E8A3 JR C,Process_Wall_Bouncing_Enemy_Advance
Search the wave enemy list for an enemy the bouncer has hit.
E8A5 INC HL Step ahead and search the wave enemy list for a collision via Find_Colliding_Wave_Enemy.
E8A6 INC HL
E8A7 CALL Find_Colliding_Wave_Enemy
E8AA JP NC,Handle_Enemy_Collision_Chain Jump to Handle_Enemy_Collision_Chain if no wave enemy collision was detected.
E8AD EXX Switch to alternate registers and step back to the bounce timer.
E8AE DEC HL
Tick down the bounce countdown; erase and redirect when it expires.
E8AF DEC HL Step to the bounce timer and subtract 04.
E8B0 LD A,(HL)
E8B1 SUB $04
E8B3 LD (HL),A
E8B4 JR NZ,Process_Wall_Bouncing_Enemy_Advance If the countdown has not reached zero, skip to Process_Wall_Bouncing_Enemy_Advance.
E8B6 LD (HL),$0C Reset the bounce countdown to 0C.
E8B8 INC HL Erase the bouncer sprite via Erase_Wide_Entity_Sprite, preserving the entity pointer.
E8B9 PUSH HL
E8BA CALL Erase_Wide_Entity_Sprite
E8BD POP HL
E8BE INC HL
Step the bouncer one pixel toward the player and pick a new heading.
E8BF LD A,($C4D4) Measure the signed Y distance to the player at Player_Y_Position.
E8C2 SUB (HL)
E8C3 JR Z,Process_Wall_Bouncing_Enemy_Step_Y Set the Y step: 01 (player below), FF (player above), or 00.
E8C5 LD A,$01
E8C7 JR NC,Process_Wall_Bouncing_Enemy_Step_Y
E8C9 LD A,$FF
Process_Wall_Bouncing_Enemy_Step_Y E8CB LD B,A Store the Y step in B, apply it to the Y position, and advance.
E8CC ADD A,(HL)
E8CD LD (HL),A
E8CE INC HL
E8CF LD A,($C4D5) Measure the signed X distance to the player at Player_X_Position.
E8D2 SUB (HL)
E8D3 JR Z,Process_Wall_Bouncing_Enemy_Step_X Set the X step: 01 (player right), FF (player left), or 00.
E8D5 LD A,$01
E8D7 JR NC,Process_Wall_Bouncing_Enemy_Step_X
E8D9 LD A,$FF
Process_Wall_Bouncing_Enemy_Step_X E8DB LD C,A Store the X step in C, apply it to the X position, and pack both step signs into a 4-bit direction code.
E8DC ADD A,(HL)
E8DD LD (HL),A
E8DE LD A,C
E8DF AND $03
E8E1 RLA
E8E2 RLA
Apply the new heading: look up the direction colour and redraw.
E8E3 LD C,A Pack the Y and X step signs into a 4-bit direction code.
E8E4 LD A,B
E8E5 AND $03
E8E7 OR C
E8E8 LD C,A
E8E9 LD B,$00
E8EB EX DE,HL Look up the heading colour from the direction table at Enemy_Direction_Code_Table.
E8EC LD HL,$EAF7
E8EF ADD HL,BC
E8F0 LD A,(HL)
E8F1 PUSH DE
E8F2 DEC DE
E8F3 DEC DE Write the heading colour to the entity record.
E8F4 LD (DE),A
E8F5 LD A,($C4E5) Look up the animation frame colour from the cycle table at Enemy_Colour_Cycle_Table.
E8F8 AND $07
E8FA LD C,A
E8FB LD B,$00
E8FD LD HL,$EA0F
E900 ADD HL,BC
E901 LD A,(HL)
E902 EX DE,HL Restore the entity pointer, set the frame colour in B', and respawn the bouncer via Draw_Wide_Entity_Sprite.
E903 EXX
E904 LD B,A
E905 EXX
E906 CALL Draw_Wide_Entity_Sprite
E909 POP HL Restore the entity pointer from the stack.
E90A INC HL Advance four bytes to the next entity record.
E90B INC HL
E90C INC HL
E90D INC HL
E90E RET Return.
This entry point is used by the routine at Handle_Enemy_Collision_Chain.
Bouncer skipped: look up the animation colour and redraw without moving.
Process_Wall_Bouncing_Enemy_Advance E90F INC HL Advance one byte, stash the pointer, and read the frame index from Colour_Cycle_Table_Pointer.
E910 PUSH HL
E911 LD A,($C4E5)
E914 AND $07
E916 LD C,A
E917 LD B,$00
E919 EX DE,HL Look up the animation colour from Enemy_Colour_Cycle_Table and set it in B'.
E91A LD HL,$EA0F
E91D ADD HL,BC
E91E LD A,(HL)
E91F EX DE,HL
E920 EXX
E921 LD B,A
E922 EXX
E923 CALL Paint_Wide_Entity_Attributes Draw the bouncer in its current position via Paint_Wide_Entity_Attributes.
E926 POP HL Restore the entity pointer from the stack.
E927 LD DE,$0006 Step six bytes to the next entity record.
E92A ADD HL,DE
E92B RET Return.
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