Routines
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42407: Check Shot Hit
Used by the routines at MoveSpark, FinishRobotTurn and MoveRobotHorizontally.
Checks whether an entity (a shot, or the robot) has run into an enemy. If it has, then both are turned into smoke and the player is awarded some points.
Input
IX Entity
Output
IY The enemy that has been hit
CheckShotHit 42407 LD B,10 There are ten enemies to check.
42409 LD IY,38608 Point IY at EnemyEntities.
CheckShotHit_Next 42413 PUSH BC Save the counter.
42414 LD A,(IY+0) Fetch the type of the enemy.
42417 AND A Jump if the entity is not in use.
42418 JR Z,CheckShotHit_Skip
42420 SUB 56 Jump if it is smoke or a sprite of a materialising enemy (types 56 to 79).
42422 CP 24
42424 JR C,CheckShotHit_Skip
42426 LD BC,49344 Use 192 as the distance in both directions.
42429 CALL ComparePositions Compare the positions using ComparePositions.
42432 JR C,CheckShotHit_Hit Jump if they overlap.
CheckShotHit_Skip 42434 LD BC,16 Each entity is 16 bytes long.
42437 ADD IY,BC Move on to the next one.
42439 POP BC Restore the counter.
42440 DJNZ CheckShotHit_Next Loop back until every enemy has been checked.
42442 RET Return.
CheckShotHit_Hit 42443 POP BC Discard the counter.
42444 LD A,(IX+0) Fetch the type of the entity that has hit the enemy...
42447 LD (IX+5),A ...and keep it.
42450 LD (38456),IY Keep the address of the enemy that was hit.
42454 LD A,(IY+0) Fetch the type of the enemy...
42457 LD (IY+5),A ...and keep it.
42460 LD A,56 Turn the shot into smoke...
42462 LD (IX+0),A
42465 LD (IY+0),A ...and the enemy too.
42468 LD BC,291 Add 291 points...
42471 JP AddPointsToScore Jump to AddPointsToScore.
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