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Routines |
| Prev: 83CA | Up: Map | Next: 845F |
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Used by the routine at HandlerKnight.
Called by the handlers of the characters. When the player enters a new room a delay of 20 is started (see CreatureDelay). Once the delay has run out, and then at random about one time in sixteen, a creature is created in a free one of the first three 16-byte records at CreatureRecords. The new record is a copy of CreatureDefaults, in the current room and with a random position. It starts as a sparkle (see HandlerSparkle) that turns into the creature chosen by FRAMES from Creatures.
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See if the player is in a different room to the last one a creature was made in.
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| SpawnCreature | 83EA | LD A,($5E26) | Fetch the room of the last creature from LastCreatureRoom and keep it in C. | |
| 83ED | LD C,A | |||
| 83EE | LD A,($EA91) | Fetch the room of the player from PlayerRoom. | ||
| 83F1 | CP C | Jump to SpawnCreature_NewRoom if the player is in a different room. | ||
| 83F2 | JR NZ,SpawnCreature_NewRoom | |||
| 83F4 | LD HL,$5E27 | Point HL at the creature delay at CreatureDelay. | ||
| 83F7 | LD A,(HL) | Fetch the creature delay. | ||
| 83F8 | AND A | Jump to SpawnCreature_Random if the delay is zero. | ||
| 83F9 | JR Z,SpawnCreature_Random | |||
| 83FB | DEC (HL) | Decrease the delay by one. | ||
| 83FC | RET NZ | Return if the delay is not zero yet. | ||
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Look for a free record for the creature, in the first three of the 16-byte records.
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| SpawnCreature_Find | 83FD | LD HL,$EE60 | Point HL at the creatures at CreatureRecords. | |
| 8400 | LD DE,$0010 | DE=0010 (the size of a record). | ||
| 8403 | LD B,$03 | B=03 (the number of records to look at). | ||
| SpawnCreature_FindLoop | 8405 | LD A,(HL) | Fetch the sprite ID of the record. | |
| 8406 | AND A | Jump to SpawnCreature_Copy if the record is free. | ||
| 8407 | JR Z,SpawnCreature_Copy | |||
| 8409 | ADD HL,DE | Move HL on to the next record. | ||
| 840A | DJNZ SpawnCreature_FindLoop | Decrease the record counter by one and loop back to SpawnCreature_FindLoop until all three records have been checked. | ||
| 840C | RET | Return. | ||
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Copy the default creature into the free record.
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| SpawnCreature_Copy | 840D | EX DE,HL | Swap DE and HL, so that DE is the free record. | |
| 840E | LD HL,$8B6A | Point HL at the creature defaults at CreatureDefaults. | ||
| 8411 | LD BC,$0010 | BC=0010 (the size of a record). | ||
| 8414 | PUSH DE | Stash the record on the stack. | ||
| 8415 | LDIR | Copy the default creature into the record. | ||
| 8417 | POP HL | Restore the record from the stack. | ||
| 8418 | PUSH HL | Stash the record on the stack again. | ||
| 8419 | INC HL | Move HL on to the room of the creature. | ||
| 841A | LD A,($EA91) | Fetch the room of the player from PlayerRoom. | ||
| 841D | LD (HL),A | Update the room of the creature. | ||
| 841E | INC HL | Move HL on to offset 02 of the creature. | ||
| 841F | PUSH HL | Stash it on the stack. | ||
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The creature that it turns into is chosen from the table using the bottom four bits of FRAMES.
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| 8420 | LD HL,$8B7A | Point HL at the creatures at Creatures. | ||
| 8423 | LD A,($5C78) | Fetch FRAMES. | ||
| 8426 | AND %00001111 | Keep only bits 0-3. | ||
| 8428 | LD E,A | Set the offset in E to the bottom four bits of FRAMES. | ||
| 8429 | LD D,$00 | Clear the high byte of the offset in D. | ||
| 842B | ADD HL,DE | Find the entry in the table of creatures. | ||
| 842C | LD A,(HL) | Fetch the sprite ID of the creature to make. | ||
| 842D | POP HL | Restore the address of offset 02 from the stack. | ||
| 842E | LD (HL),A | Set the type of the creature at offset 02. | ||
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Choose a random X and Y position inside the room.
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| 842F | LD DE,($5E1D) | Fetch the size of the room from CurrentRoom_Width. | ||
| 8433 | LD B,E | Set the limit for the X position in B to the width of the room. | ||
| 8434 | CALL GetRandomCoordinate | Call GetRandomCoordinate to pick a random coordinate. | ||
| 8437 | LD (HL),A | Update the X position of the creature. | ||
| 8438 | LD B,D | Set the limit for the Y position in B to the height of the room. | ||
| 8439 | CALL GetRandomCoordinate | Call GetRandomCoordinate to pick a random coordinate. | ||
| 843C | LD (HL),A | Update the Y position of the creature. | ||
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Give the creature a random velocity and draw it.
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| 843D | POP DE | Restore the address of the record from the stack. | ||
| 843E | PUSH IX | Stash the current entity on the stack. | ||
| 8440 | LD IX,$0000 | Make IX point at the new creature (copy DE to IX). | ||
| 8444 | ADD IX,DE | |||
| 8446 | CALL RandomiseVelocity | Call RandomiseVelocity to give the creature a new random velocity. | ||
| 8449 | CALL DrawEntity | Call DrawEntity to draw the sparkle. | ||
| 844C | POP IX | Restore the current entity from the stack. | ||
| 844E | RET | Return. | ||
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The player is in a new room, so remember the room and start the delay.
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| SpawnCreature_NewRoom | 844F | LD ($5E26),A | Update the room of the last creature in LastCreatureRoom. | |
| 8452 | LD A,$20 | Write 20 to CreatureDelay. | ||
| 8454 | LD ($5E27),A | |||
| 8457 | RET | Return. | ||
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There is no delay, so only make a creature one time in sixteen.
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| SpawnCreature_Random | 8458 | LD A,R | Fetch a random number (from the refresh register). | |
| 845A | AND %00001111 | Keep only bits 0-3. | ||
| 845C | RET NZ | Return if the result is not zero. | ||
| 845D | JR SpawnCreature_Find | Jump back to SpawnCreature_Find to look at the next record. | ||
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