Routines
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48444: Update Thing Upstairs Movement
Used by the routine at ScriptRoutine_ThingUpstairsChase.
Move the Thing Upstairs entity toward Berk within its room bounds and queue a chase sound when it closes in.
Input
IX Address of complex state data for an entity
Update_ThingUpstairs_Movement 48444 LD A,10 Load A with 10.
48446 CALL PseudoRandom Call PseudoRandom to pick a pseudo-random value.
48449 ADD A,5 Add 5 to A (adjust an entity/timer value).
48451 LD (48095),A Set Thing Upstairs flag byte (48095).
48454 LD A,2 Load A with 2.
48456 CALL PseudoRandom Call PseudoRandom to pick a pseudo-random value.
48459 INC A Advance 2 by one.
48460 ADD A,A Multiply A by 4 to form a table index.
48461 ADD A,A
48462 LD C,A Keep 2 in C for later.
48463 LD A,4 Load A with 4.
48465 CALL PseudoRandom Call PseudoRandom to pick a pseudo-random value.
48468 INC A Advance 4 by one.
48469 CP 3 Is 4 less than 3? If not, jump to Update_ThingUpstairs_Movement_TrackBerkX.
48471 JR NC,Update_ThingUpstairs_Movement_TrackBerkX
48473 OR C Merge another flag byte into 4.
48474 LD A,C Copy the saved count/flag from C into A.
48475 JR Update_ThingUpstairs_Movement_StoreState Jump to Update_ThingUpstairs_Movement_StoreState to store the Thing Upstairs direction.
Steer toward Berk on X: face right if aligned, else face left.
Update_ThingUpstairs_Movement_TrackBerkX 48477 LD A,(29443) Load A with Berk's X-coordinate copy (BerkXCoordinateCopy).
48480 LD B,A Keep Berk's X-coordinate copy in B for later.
48481 LD A,(IX+7) Load A with the current entity's x-coordinate.
48484 CP B Does this entity's x equal B? If not, jump to Update_ThingUpstairs_Movement_FaceRight.
48485 JR NC,Update_ThingUpstairs_Movement_FaceRight
48487 SET 0,C Set bit 0 of the saved flags in C.
48489 JR Update_ThingUpstairs_Movement_WriteDirection Jump to Update_ThingUpstairs_Movement_WriteDirection to keep the Thing Upstairs direction flags.
Face left when the Thing Upstairs entity's X does not match Berk's copy at BerkXCoordinateCopy.
Update_ThingUpstairs_Movement_FaceRight 48491 SET 1,C Set bit 1 of the saved flags in C.
Commit the chosen chase direction flags into A.
Update_ThingUpstairs_Movement_WriteDirection 48493 LD A,C Copy the saved count/flag from C into A.
Store the chase direction/state back onto the Thing Upstairs entity.
Update_ThingUpstairs_Movement_StoreState 48494 LD (IX+9),A Set the current entity's direction / state.
48497 RET Return.
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