Routines
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7633: UFO Abduct Percy
Used by the routine at Handler_UFO.
Handles the UFO's abduction of Percy. Teleports Percy to the UFO's position while playing a tractor beam sound effect, then on the final frame drops Percy downward.
Input
IX Pointer to UFO sprite data
UFO_Abduct_Percy 7633 CP $01 Jump to UFO_Drop_Percy if the abduction timer is equal to 01 (final frame of abduction).
7635 JR Z,UFO_Drop_Percy
Play the tractor beam sound effect.
7637 LD HL,$767F Point HL at UFO_Tractor_Beam_Pitch (tractor beam sound pitch).
763A LD E,(HL) Load the pitch into E and C.
763B LD C,(HL)
Tractor_Beam_SoundStep_Loop 763C LD B,E Copy to B.
763D LD A,$01 Set initial speaker state to 01.
Tractor_Beam_Sound_Inner 763F NOP Action a delay loop.
7640 DJNZ Tractor_Beam_Sound_Inner
7642 XOR %00011000 Toggle the speaker bits and output to the speaker port.
7644 OUT ($FE),A
7646 DEC C Decrement C and loop back to Tractor_Beam_SoundStep_Loop until the sound step is complete.
7647 JR NZ,Tractor_Beam_SoundStep_Loop
7649 LD A,(HL) Complement and mask the pitch value.
764A CPL
764B AND %00111111
764D LD (HL),A Write back to *HL.
Teleport Percy to the UFO's position.
764E LD A,(IX+$00) Copy the UFO's X position to Percy's X at *Percy_X_Position.
7651 LD ($DAC0),A
7654 LD A,(IX+$01) Copy the UFO's Y position plus 0A to Percy's Y at *Percy_Y_Position.
7657 ADD A,$0A
7659 LD ($DAC1),A
765C LD A,(IX+$02) Copy the UFO's sprite active value to Percy's at *Percy_Colour.
765F LD ($DAC2),A
7662 XOR A Write 00 to clear *FallingState.
7663 LD ($5FA7),A
7666 JP CancelEggDrop Jump to CancelEggDrop.
Final frame of abduction; drop Percy downward.
UFO_Drop_Percy 7669 LD A,($DAC1) Add 14 to Percy's Y position at *Percy_Y_Position.
766C ADD A,$14
766E LD ($DAC1),A
7671 LD ($5FA7),A Write the result to *FallingState (set collision flag).
7674 XOR A Write 00 to clear *UFO_Abduction_Timer.
7675 LD ($767E),A
7678 RET Return.
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