Routines
Prev: 8CBC Up: Map Next: 8E5A
8D06: Handler: Jetman Movement
Read the controls, spend fuel when flying, and update Jetman's facing and animation.
Input
IX Actor slot
Face Jetman from LEFT/ RIGHT, or coast the current horizontal speed toward a rest.
Handler_JetmanMovement 8D06 CALL HandlerControls Call HandlerControls.
8D09 BIT 1,A Jump to FaceJetmanLeft if LEFT is pressed.
8D0B JP Z,FaceJetmanLeft
8D0E BIT 0,A Jump to FaceJetmanRight if RIGHT is pressed.
8D10 JP Z,FaceJetmanRight
8D13 LD A,(IX+$05) Jump to Handler_JetmanMovement_Read if the horizontal speed is zero.
8D16 AND A
8D17 JR Z,Handler_JetmanMovement_Read
8D19 JP P,Handler_JetmanMovement_CoastRight Jump to Handler_JetmanMovement_CoastRight if Jetman is moving right.
Coast a leftward speed back toward rest.
8D1C ADD A,$02 Add 02 to the speed.
8D1E CP $D0 Jump to Handler_JetmanMovement_Grounded if it is now less than D0.
8D20 JR C,Handler_JetmanMovement_Grounded
8D22 CP $E0 Jump to Handler_JetmanMovement_Grounded if it is at least E0.
8D24 JR NC,Handler_JetmanMovement_Grounded
8D26 ADD A,$10 Add a further 10 to leave the mid-band.
8D28 JR Handler_JetmanMovement_Grounded Jump to Handler_JetmanMovement_Grounded.
Coast a rightward speed back toward rest.
Handler_JetmanMovement_CoastRight 8D2A ADD A,$FE Decrease the speed by 02.
8D2C CP $40 Jump to Handler_JetmanMovement_Grounded if it is now at least 40.
8D2E JR NC,Handler_JetmanMovement_Grounded
8D30 CP $30 Jump to Handler_JetmanMovement_Grounded if it is less than 30.
8D32 JP C,Handler_JetmanMovement_Grounded
8D35 SUB $10 Subtract a further 10 to leave the mid-band.
This entry point is used by the routines at FaceJetmanRight and FaceJetmanLeft.
Handler_JetmanMovement_Grounded 8D37 LD (IX+$05),A Write the speed to *IX+05.
Read the thrust keys while any fuel remains.
Handler_JetmanMovement_Read 8D3A CALL HandlerControls Call HandlerControls.
8D3D LD B,A Stash the controls in B.
8D3E LD A,($608F) Jump to Handler_JetmanMovement_Gravity if FuelLevel_2 is zero.
8D41 AND A
8D42 JR Z,Handler_JetmanMovement_Gravity
8D44 BIT 3,B Jump to ApplyJetmanUpwardThrust if UP is pressed.
8D46 JP Z,ApplyJetmanUpwardThrust
8D49 BIT 2,B Jump to ClearJetmanThrust if DOWN is pressed.
8D4B JP Z,ClearJetmanThrust
Apply gravity when Jetman is not thrusting.
Handler_JetmanMovement_Gravity 8D4E LD B,$00 Clear the fuel-spend base.
8D50 LD A,(IX+$06) Jump to Handler_JetmanMovement_ThrustStep if the vertical thrust is negative.
8D53 AND A
8D54 JP M,Handler_JetmanMovement_ThrustStep
8D57 CP $40 Jump to Handler_JetmanMovement_Loop if the downward thrust is already at least 40.
8D59 JR NC,Handler_JetmanMovement_Loop
The gravity step is 08 (signed +08). Upward thrust uses the opposite F8.
Handler_JetmanMovement_ThrustStep 8D5B LD C,$08 Set the downward step to 08.
This entry point is used by the routine at ApplyJetmanUpwardThrust.
Handler_JetmanMovement_AddThrust 8D5D ADD A,C Add the step to the vertical thrust.
8D5E LD (IX+$06),A
Convert the thrust into a Y offset and test for the ground or a crater.
Handler_JetmanMovement_Loop 8D61 LD A,(IX+$06) Fetch the vertical thrust.
8D64 SRA A Divide it by 10.
8D66 SRA A
8D68 SRA A
8D6A SRA A
8D6C ADD A,(IX+$04) Add it to Jetman's Y position.
8D6F CP $40 Jump to ClearJetmanThrust if Jetman is above the play area.
8D71 JP C,ClearJetmanThrust
8D74 CP $B0 Jump to Handler_JetmanMovement_WriteY if Jetman is still above the ground line.
8D76 JR C,Handler_JetmanMovement_WriteY
Check the terrain beneath Jetman's new position.
8D78 CALL ReadTerrainCell Call ReadTerrainCell.
8D7B LD A,D Jump to Handler_JetmanMovement_ClampThrust if the first terrain cell is empty.
8D7C AND A
8D7D JR Z,Handler_JetmanMovement_ClampThrust
8D7F LD A,E Jump to Handler_JetmanMovement_ClampThrust if the second terrain cell is empty.
8D80 AND A
8D81 JR Z,Handler_JetmanMovement_ClampThrust
8D83 LD A,E Jump to LandJetman if neither cell has bit 3 set (a crater).
8D84 OR D
8D85 BIT 3,A
8D87 JP Z,LandJetman
When the cell is empty or a crater, snap to the ground line at Y=AF and give a small upward thrust of E0 (signed -20).
Handler_JetmanMovement_ClampThrust 8D8A LD (IX+$06),$E0 Write E0 to the vertical thrust.
8D8E LD A,$AF A=AF.
Handler_JetmanMovement_WriteY 8D90 LD (IX+$04),A Write the Y position to *IX+04.
Spend fuel from the horizontal speed, then redraw the gauge.
Handler_JetmanMovement_FuelFromSpeed 8D93 LD A,(IX+$05) Jump to Handler_JetmanMovement_HalveSpeed if the horizontal speed is positive.
8D96 AND A
8D97 JP P,Handler_JetmanMovement_HalveSpeed
8D9A NEG Negate it so the spend uses the magnitude.
Handler_JetmanMovement_HalveSpeed 8D9C SRA A Halve the speed.
8D9E ADD A,B Add the fuel-spend base.
8D9F SLA A Double the result.
8DA1 LD C,A Store the spend in BC.
8DA2 LD B,$00
8DA4 LD HL,($608E) Fetch the current fuel from FuelLevel_1.
8DA7 LD A,H Jump to Handler_JetmanMovement_AfterFuel if the fuel has already run out.
8DA8 OR L
8DA9 JR Z,Handler_JetmanMovement_AfterFuel
8DAB AND A Reset the carry flag.
Subtract the fuel expenditure from the current fuel level.
See Infinite Fuel.
Handler_JetmanMovement_SpendFuel 8DAC SBC HL,BC Subtract the spend from the fuel.
8DAE LD A,H Jump to Handler_JetmanMovement_AfterFuel if the high fuel byte is not zero.
8DAF AND A
8DB0 JR NZ,Handler_JetmanMovement_AfterFuel
Queue a tune and empty the tank when the fuel is used up.
8DB2 LD DE,$BA2D DE=Tune_Out_Of_Fuel.
8DB5 CALL QueueTune Call QueueTune.
8DB8 LD HL,$0000 HL=0000.
Store the remaining fuel and redraw the gauge.
Handler_JetmanMovement_AfterFuel 8DBB LD ($608E),HL Write the remaining fuel to FuelLevel_1.
8DBE LD A,H Fetch the high fuel byte.
8DBF LD HL,$1040 HL=1040 (gauge position).
8DC2 CALL DrawGauge Call DrawGauge.
Walk the 0-based sprite index: keep bits 2-7 (facing and flying/ walking) and merge bits 0-1 from the frame timer.
Handler_JetmanMovement_Animate 8DC5 CALL ApplyJetmanSpeed Call ApplyJetmanSpeed.
8DC8 LD A,($5E42) Fetch GameTimer.
8DCB AND %00000011 Keep only bits 0-1.
8DCD LD C,A Stash the frame bits.
8DCE LD A,(IX+$00) Fetch the actor type.
8DD1 DEC A Decrease it to a 0-based sprite index.
8DD2 AND %11111100 Keep only bits 2-7.
8DD4 OR C Merge in the frame bits.
8DD5 INC A Restore the 1-based sprite ID.
8DD6 LD (IX+$00),A Write it back to *IX+00.
Draw Jetman and fire the laser when FIRE is held.
Handler_JetmanMovement_Draw 8DD9 CALL DrawSprite Call DrawSprite.
8DDC CALL ColouriseSprite Call ColouriseSprite.
8DDF CALL HandlerControls Call HandlerControls.
8DE2 BIT 4,A Call Handler_LaserBeam if FIRE is pressed.
8DE4 CALL Z,Handler_LaserBeam
Queue a flying jingle on some frames.
8DE7 LD A,($FF54) Jump to Handler_JetmanMovement_RefillFromRover if Tune_Pointer is not Tune_Buffer_End.
8DEA CP $51
8DEC JR NZ,Handler_JetmanMovement_RefillFromRover
8DEE LD A,($5E40) Fetch RandomNumber.
8DF1 AND %01111111 Keep only bits 0-6.
8DF3 JR NZ,Handler_JetmanMovement_RefillFromRover Jump to Handler_JetmanMovement_RefillFromRover if the result is not zero.
Pick a jingle from the table using the game timer and queue it.
8DF5 LD A,($5E42) Fetch GameTimer.
8DF8 AND %00001110 Keep only bits 1-3.
8DFA LD C,A Convert that index into BC.
8DFB LD B,$00
8DFD LD HL,$9DB0 Point HL at the matching entry in Jetman_Tune_Table.
8E00 ADD HL,BC
8E01 LD E,(HL) Fetch the tune pointer.
8E02 INC HL
8E03 LD D,(HL)
8E04 CALL QueueTune Call QueueTune.
Refill the tank when Jetman is beside the rover, then take a platform (action key) or board (SPACE).
Handler_JetmanMovement_RefillFromRover 8E07 LD A,(IX+$04) Fetch Jetman's Y position.
8E0A CP $A8 Return if it is less than A8.
8E0C RET C
Return unless the rover is on this screen and within reach.
8E0D LD HL,($607A) Fetch Jetman_Position.
8E10 LD DE,($6092) Fetch Rover_Position.
8E14 AND A Subtract the rover position from Jetman's.
8E15 SBC HL,DE
8E17 LD DE,$000C Add a 0C tolerance.
8E1A ADD HL,DE
8E1B LD A,H Fetch the high byte of the gap.
8E1C AND %00011111 Keep only bits 0-4.
8E1E RET NZ Return if the rover is not on this screen.
8E1F LD A,L Return if the low byte is at least 18.
8E20 CP $18
8E22 RET NC
Refill the fuel tank.
8E23 LD HL,$9000 Write 9000 to FuelLevel_1.
8E26 LD ($608E),HL
Bit 0 of Jetman's flags is set while he is carrying an item.
8E29 BIT 0,(IX+$08) Return if Jetman is already carrying an item.
8E2D RET NZ
8E2E CALL TestActionKey Jump to Handler_JetmanMovement_TestSpace if the action key is not pressed.
8E31 JR Z,Handler_JetmanMovement_TestSpace
8E33 LD HL,$60F0 HL=World_Slot_4.
8E36 LD A,(HL) Return if world slot 4 is already in use.
8E37 AND A
8E38 RET NZ
Type 2E is the platform Jetman now carries.
8E39 LD (HL),$2E Write type 2E to the slot.
8E3B LD DE,$0007 Move to the colour byte.
8E3E ADD HL,DE
8E3F LD (HL),$43 Write INK:MAGENTA, PAPER:BLACK (BRIGHT) to the colour.
8E41 INC HL Set bit 0 of the slot flags.
8E42 SET 0,(HL)
8E44 INC HL Write 00 to *HL+02.
8E45 INC HL
8E46 LD (HL),$00
8E48 SET 0,(IX+$08) Set bit 0 of Jetman's flags.
8E4C JP SoundsTakeObject Jump to SoundsTakeObject.
Board the rover if SPACE is pressed.
Handler_JetmanMovement_TestSpace 8E4F CALL TestSpaceKey Return if SPACE is not pressed.
8E52 RET Z
8E53 CALL PositionAndDrawSprite Call PositionAndDrawSprite.
8E56 CALL BoardMoonRover Call BoardMoonRover.
8E59 RET Return.
Prev: 8CBC Up: Map Next: 8E5A