Routines
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36397: Apply Collision Effects
Used by the routine at UpdateEnemies.
Works out what happens when the player's ship hits an object. The object sets the byte at 36396 when it is updated, and each bit of that byte selects an effect:
Bit Effect
7 Slow the ship down (SlowShip)
6 Damage the ship (DamageShip)
5 Drain fuel (DrainFuel)
4 Bounce the ship (BounceShip)
3 Mark the object as destroyed (DestroyObject)
2 Add fuel (AddFuel)
1 Add a ship (AddShip)
0 Mark the object as hit (MarkObjectHit)
Input
IX Address of the object
ApplyCollisionEffects 36397 LD A,(38571) Fetch the flag from 38571.
36400 AND A Test it.
36401 RET NZ Return if it is set.
36402 LD A,(36691) Fetch the explosion counter from 36691.
36405 AND A Test it.
36406 RET NZ Return if the ship is exploding.
36407 LD A,(36396) Fetch the collision effects from 36396.
36410 AND A Test them.
36411 RET Z Return if there are none.
36412 LD A,(41432) Fetch the collision flag from 41432.
36415 AND A Test it.
36416 RET Z Return if there is no collision.
36417 LD IX,(44358) Fetch the address of the object that was hit from CurrentObject.
36421 BIT 3,(IX+23) Test bit 3 of its second set of flags.
36425 RET NZ Return if it is set.
36426 LD L,(IX+17) Fetch the screen position of the object into HL.
36429 LD H,(IX+18)
36432 LD IX,43940 Use the hit data at CollisionBox.
36436 LD (IX+3),A Store the collision effects in the hit data.
36439 LD A,L Fetch the horizontal screen position.
36440 CP 142 Is it 142 or more?
36442 RET NC Return if so.
36443 CP 40 Is it lower than 40?
36445 RET C Return if so.
36446 LD (IX+0),L Store the screen position in the hit data.
36449 LD (IX+1),H
36452 LD A,(23593) Fetch the value from 23593.
36455 LD (IX+2),A Store it in the hit data.
36458 LD A,(23608) Fetch the value from ShipRow.
36461 ADD A,8 Add eight.
36463 LD H,A Use it as the vertical position.
36464 LD L,100 Set the horizontal position to 100.
36466 LD D,40 Set the width to 40...
36468 LD E,16 ...and the height to 16.
36470 CALL TestBoxesOverlap Check for a hit.
36473 LD IX,(44358) Bring IX back from CurrentObject.
36477 LD IY,51429 Use the player's object.
36481 LD A,(23580) Fetch the value from ScratchValue.
36484 AND A Test it.
36485 JP Z,ApplyPlayerCollision Jump to ApplyPlayerCollision if it is zero.
36488 LD A,128 Set CollisionKind to 128.
36490 LD (53436),A
36493 LD A,(36396) Fetch the collision effects from 36396.
36496 LD C,A Copy them into C.
36497 INC A Increment them.
36498 JR NZ,ApplyCollisionEffects_Bit7 Jump to ApplyCollisionEffects_Bit7 if they were not 255.
36500 DEC A Make 35183 255.
36501 LD (35183),A
36504 SET 4,(IX+16) Set bit 4 of the flags of the object.
36508 JP PlayHitSound Play the explosion sound.
ApplyCollisionEffects_Bit7 36511 BIT 7,C Test bit 7.
36513 CALL NZ,SlowShip Slow the ship down if it is set.
36516 BIT 6,C Test bit 6.
36518 CALL NZ,DamageShip Damage the ship if it is set.
36521 BIT 5,C Test bit 5.
36523 CALL NZ,DrainFuel Drain the fuel if it is set.
36526 BIT 4,C Test bit 4.
36528 CALL NZ,BounceShip Bounce the ship if it is set.
36531 BIT 3,C Test bit 3.
36533 CALL NZ,DestroyObject Mark the object as destroyed if it is set.
36536 BIT 2,C Test bit 2.
36538 CALL NZ,AddFuel Add fuel if it is set.
36541 PUSH BC Save the effects.
36542 BIT 1,C Test bit 1.
36544 CALL NZ,AddShip Add a ship if it is set.
36547 POP BC Restore the effects.
36548 BIT 0,C Jump to MarkObjectHit if bit 0 is set.
36550 JP NZ,MarkObjectHit
36553 RET Return.
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