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Routines |
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The address stored at 34246 is the address of complex state data for the entity to start with when doing collision checks in reverse order. On levels 2, 3 and 4, the value stored here is the address of the complex state data of the last entity, which means that on these levels, all entities are checked. On level 1, however, the value stored is the address of the complex state data of the sixth-last entity. The remaining five entities after this address on level 1 are the three spiders, their webs and their arches. This means that on level 1, these spiders, webs and arches are excluded from certain collision checks.
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| 54890 | LD C,1 | Set depth offset to 1 (i.e. check entities at next depth level into screen) | ||||||||||||||||
| 54892 | LD DE,65523 | Load DE with -13 (as entries in complex state data are 13 bytes wide) | ||||||||||||||||
| 54895 | LD IY,(34246) | Load IY with current level's start address for reverse-order collision checks | ||||||||||||||||
| 54899 | LD A,(IX+0) | If room of entity at IX is not the same as room of entity at IY... | ||||||||||||||||
| 54902 | CP (IY+0) | ... | ||||||||||||||||
| 54905 | JR NZ,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54907 | BIT 5,(IY+10) | If current entity at IY has its is-being-carried flag set... | ||||||||||||||||
| 54911 | JP NZ,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54914 | LD A,(IY+8) | If current entity at IY has a class which is the same as the entity at IX... | ||||||||||||||||
| 54917 | CP (IX+8) | ... | ||||||||||||||||
| 54920 | JR Z,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54922 | BIT 7,A | If entity at IY has its spans-full-depth flag set... | ||||||||||||||||
| 54924 | JR NZ,54935 | ...then skip over depth check to 54935 | ||||||||||||||||
| 54926 | LD A,(IY+1) | If entity at IY has a depth which is not the same as the depth of the entity at IX... | ||||||||||||||||
| 54929 | SUB C | ...minus depth offset... | ||||||||||||||||
| 54930 | CP (IX+1) | ... | ||||||||||||||||
| 54933 | JR NZ,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54935 | LD A,(IY+11) | If entity at IY has its interaction-(11,7) flag reset... | ||||||||||||||||
| 54938 | AND 128 | ... | ||||||||||||||||
| 54940 | JP Z,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54943 | LD A,(IX+6) | If the bottom of the entity at IX... | ||||||||||||||||
| 54946 | CP (IY+4) | ...is above the top of the entity at IY... | ||||||||||||||||
| 54949 | JR C,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54951 | LD A,(IY+6) | If the bottom of the entity at IY... | ||||||||||||||||
| 54954 | CP (IX+4) | ...is above the top of the entity at IX... | ||||||||||||||||
| 54957 | JR C,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54959 | LD A,(IX+7) | If the right side of entity IX... | ||||||||||||||||
| 54962 | CP (IY+5) | ...is to the left of the left side of the entity at IY... | ||||||||||||||||
| 54965 | JR C,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54967 | LD A,(IY+7) | If the right side of entity IY... | ||||||||||||||||
| 54970 | CP (IX+5) | ...is to the left of the left side of the entity at IX... | ||||||||||||||||
| 54973 | JR C,54987 | ...then move IY back to previous entity | ||||||||||||||||
| 54975 | XOR A | Set A to zero to reset carry flag | ||||||||||||||||
| 54976 | LD (34258),IY | Store pointer to current entity at 34258 | ||||||||||||||||
| 54980 | LD A,(IY+8) | Load A with class of entity at IY | ||||||||||||||||
| 54983 | RET | Return | ||||||||||||||||
| 54984 | LD DE,65523 | Load DE with -13 | ||||||||||||||||
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This entry point is used by the routine at 54878.
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| 54987 | LD A,(IY-1) | If byte before current IY position is 254 (i.e. end marker for simple state data)... | ||||||||||||||||
| 54990 | CP 254 | ... | ||||||||||||||||
| 54992 | JP Z,55000 | ...then skip ahead to 55000 | ||||||||||||||||
| 54995 | ADD IY,DE | Move IY back 13 bytes (i.e. to start of previous entry) | ||||||||||||||||
| 54997 | JP 54899 | Jump to 54899 | ||||||||||||||||
| 55000 | SCF | Set carry flag | ||||||||||||||||
| 55001 | RET | Return | ||||||||||||||||
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