Routines
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58056: Pick Random Spawn Position
Used by the routines at Spawn_Horizontal_Wave_Enemies, Spawn_Tracked_Enemy_Entities and Spawn_Wall_Bouncing_Enemies.
Generates a random Y coordinate in the range 16-167 and a random X coordinate in the range 8-231 writing both to *HL with initial velocities 16/16 then tests whether the chosen position overlaps the player spawn zone via HitTestBounds8AtHL; retries the whole selection if it does. Called from Spawn_Horizontal_Wave_Enemies and Spawn_Wall_Bouncing_Enemies.
Pick_Random_Spawn_Position_Y 58056 CALL Generate_Random_Byte Generate random bytes until a valid Y coordinate (16-167) is found and write it to *HL.
58059 CP 16
58061 JP C,Pick_Random_Spawn_Position_Y
58064 CP 168
58066 JP NC,Pick_Random_Spawn_Position_Y
58069 LD (HL),A
58070 INC HL
Pick_Random_Spawn_Position_X 58071 CALL Generate_Random_Byte Generate random bytes until a valid X coordinate (8-231) is found and write it to *HL.
58074 CP 8
58076 JP C,Pick_Random_Spawn_Position_X
58079 CP 232
58081 JP NC,Pick_Random_Spawn_Position_X
58084 LD (HL),A
58085 INC HL Write initial Y and X velocities (16 each) to the entity record.
58086 LD (HL),16
58088 INC HL
58089 LD (HL),16
58091 DEC HL Step back three bytes and set the player spawn area address in alternate HL via Entity_Spawn_Handler.
58092 DEC HL
58093 DEC HL
58094 EXX
58095 LD HL,53703
58098 EXX
58099 CALL HitTestBounds8AtHL Test whether the position overlaps the player spawn zone via HitTestBounds8AtHL; return if clear.
58102 RET C
58103 DEC HL Retry the whole position selection from Pick_Random_Spawn_Position_Y if it overlaps.
58104 DEC HL
58105 DEC HL
58106 JP Pick_Random_Spawn_Position_Y
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