Entity: Difference between revisions
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Piranhaplant (talk | contribs) (Created page with "Entities are used to run multiple distinct things at the same time through a cooperative multitasking system. Almost all code in the game is run as part of an entity. Monsters, the players, weapon projectiles, and even the main game loop are separate entities. == Overview == Each entity is allocated the following: * 0x80 bytes in RAM. The direct page will be set to this area, so it can be accessed with $00-$7F. * 0x30 bytes of stack. An entity is created by calling ...") |
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An entity is created by calling [[$80:825E]] and providing a pointer to the start of the entity code in the Y register and accumulator. Upon creation, 10 bytes ($00-$09) are copied from the current direct page to the direct page of the new entity. This can be used to provide various parameters to the entity.
[[$80:8353]] is called to yield control to other entities. The accumulator contains the number of frames before this entity is resumed. Control resumes immediately following the call to $80:8353. Yielding control will preserve the data bank register, processor status register, and direct page register by pushing them onto the stack in that order. No other registers are preserved.
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