Routines
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45413: Set Speed Towards Player
Used by the routines at HandleChasingDome and HandleHomingSparkle.
Sets the speed of an object along the x and y axes so that it heads towards the player.
Input
B Speed along the y axis
C Speed along the x axis
IX The address of the object
Head towards the player along each axis.
SetSpeedTowardsPlayer 45413 LD HL,23433 Point HL at 23433.
45416 LD A,(IX+1) Fetch the x position of the object.
45419 SUB (HL) Subtract the player's x position.
45420 INC HL Move on to the y position.
45421 LD A,C Fetch the speed along the x axis.
45422 JP M,SetSpeedTowardsPlayer_SetX Jump to SetSpeedTowardsPlayer_SetX if the object is west of the player.
45425 NEG Make the speed negative.
SetSpeedTowardsPlayer_SetX 45427 LD (IX+9),A Set the speed along the x axis.
45430 LD A,(IX+2) Fetch the y position of the object.
45433 SUB (HL) Subtract the player's y position.
45434 INC HL Move on.
45435 LD A,B Fetch the speed along the y axis.
45436 JP M,SetSpeedTowardsPlayer_SetY Jump to SetSpeedTowardsPlayer_SetY if the object is south of the player.
45439 NEG Make the speed negative.
SetSpeedTowardsPlayer_SetY 45441 LD (IX+10),A Set the speed along the y axis.
45444 RET Return.
View the equivalent code in;
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