Routines
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58059: Handle Carrying Eagle
Handler for the object types 92 to 95 an eagle that carries Sabreman (see Handle_Flying_Creature). Bit 0 of the type is the frame of the animation, which follows bit 1 of the tick counter, and bit 1 is set when the x velocity is negative.
While Sabreman is being carried his record has the sprite id 96 to 99. The eagle puts his position in bytes 8 (x) and 9 (y) of his record (at Sabreman_Carried_X_Position and Sabreman_Carried_Y_Position), where Handle_Carried_Sabreman picks it up. The y position is 16 more than that of the eagle, so he hangs below it.
The eagle flies towards a target (byte 12 is the x position and byte 14 the y position, see Choose_Eagle_Target). Each call changes each velocity by one towards the target. The x velocity is kept between 208 and 55 and the y velocity between 199 and 55. The target changes when the eagle bounces off a decoration, a bubble, the floor, the ceiling or a wall. The eagle can also fly through the gaps in the frame of a room, and into the next room. The player can nudge the eagle with the controls (see Steer_Eagle).
The eagle lets go (see Check_Eagle_Release) when the low byte of FRAMES is zero, or when Sabreman has set bit 5 of his redraw flags, if it is in the open part of the room. If the sprite id of Sabreman is less than 28 (he is not being carried), the eagle lets go at once (see Release_Sabreman).
Input
IX Object record of the eagle
Handle_Carrying_Eagle 58059 CALL StoreEntity Save the state of the eagle.
58062 LD A,(36634) Fetch the sprite id of Sabreman.
58065 CP 28 Jump to Release_Sabreman if he is not being carried.
58067 JP C,Release_Sabreman
58070 CALL Steer_Eagle Nudge the eagle if the player presses a direction.
58073 CALL Read_World_Map Read the world map entry of the room that the eagle is in. The flags of the room are returned in E.
58076 LD A,(23672) Fetch the low byte of FRAMES.
58079 AND A Call Check_Eagle_Release to let go of Sabreman if the low byte of FRAMES is zero.
58080 CALL Z,Check_Eagle_Release
58083 LD A,(36649) Fetch the redraw flags of Sabreman.
58086 BIT 5,A Test bit 5, which Sabreman sets to ask the eagle to let go.
58088 RES 5,A Reset bit 5.
58090 LD (36649),A Store the redraw flags of Sabreman.
58093 CALL NZ,Check_Eagle_Release Call Check_Eagle_Release to let go of Sabreman if bit 5 was set.
This entry point is used by the routine at Handle_Flying_Creature.
Handle_Carrying_Eagle_Carry 58096 LD A,1 Set the flag at Type_5C_Active_Flag to show that an eagle is carrying Sabreman.
58098 LD (36593),A
58101 LD A,(IX+3) Fetch the y position of the eagle.
58104 ADD A,16 Add 16.
58106 CP 159 Jump to Handle_Carrying_Eagle_Set_Carry_Position if the result is less than 159.
58108 JR C,Handle_Carrying_Eagle_Set_Carry_Position
58110 BIT 4,E Jump to Handle_Carrying_Eagle_Set_Carry_Position if the room has no floor.
58112 JR Z,Handle_Carrying_Eagle_Set_Carry_Position
58114 LD A,159 Limit the y position to 159.
Handle_Carrying_Eagle_Set_Carry_Position 58116 LD (36643),A Set the y position of Sabreman.
58119 LD A,(IX+1) Fetch the x position of the eagle.
58122 LD (36642),A Set the x position of Sabreman.
Work out the type of the eagle. Bit 0 follows bit 1 of the tick counter and bit 1 is set when the x velocity is negative.
58125 LD A,(IX+0) Fetch the type of the eagle.
58128 AND %11111110 Reset bit 0.
58130 LD C,A Keep the type without bit 0 in C.
58131 LD A,(36566) Fetch the tick counter.
58134 RRA Move bit 1 into bit 0.
58135 AND %00000001 Keep only that bit.
58137 ADD A,C Add the type.
58138 BIT 7,(IX+8) Jump to Handle_Carrying_Eagle_Face_Right if the x velocity is positive.
58142 JR Z,Handle_Carrying_Eagle_Face_Right
58144 OR %00000010 Set bit 1.
58146 JR Handle_Carrying_Eagle_Store_Type Jump to Handle_Carrying_Eagle_Store_Type.
Handle_Carrying_Eagle_Face_Right 58148 AND %11111101 Reset bit 1.
Handle_Carrying_Eagle_Store_Type 58150 LD (IX+0),A Store the type of the eagle.
Change the x velocity by one towards the target.
58153 LD A,(IX+1) Fetch the x position of the eagle.
58156 CP (IX+12) Compare it with the x position of the target.
58159 LD A,(IX+8) Fetch the x velocity.
58162 JP NC,Accelerate_Eagle_Left Jump to Accelerate_Eagle_Left if the eagle is at or to the right of the target.
58165 INC A Add one to the x velocity.
58166 BIT 7,A Jump to Handle_Carrying_Eagle_Store_X_Velocity if the x velocity is negative.
58168 JR NZ,Handle_Carrying_Eagle_Store_X_Velocity
58170 CP 56 Jump to Handle_Carrying_Eagle_Adjust_Y_Velocity if the x velocity has reached 56.
58172 JR NC,Handle_Carrying_Eagle_Adjust_Y_Velocity
This entry point is used by the routine at Accelerate_Eagle_Left.
Handle_Carrying_Eagle_Store_X_Velocity 58174 LD (IX+8),A Store the x velocity.
This entry point is used by the routine at Accelerate_Eagle_Left.
Change the y velocity by one towards the target.
Handle_Carrying_Eagle_Adjust_Y_Velocity 58177 LD A,(IX+3) Fetch the y position of the eagle.
58180 CP (IX+14) Compare it with the y position of the target.
58183 LD A,(IX+9) Fetch the y velocity.
58186 JP NC,Accelerate_Eagle_Up Jump to Accelerate_Eagle_Up if the eagle is at or below the target.
58189 INC A Add one to the y velocity.
58190 BIT 7,A Jump to Handle_Carrying_Eagle_Store_Y_Velocity if the y velocity is negative.
58192 JR NZ,Handle_Carrying_Eagle_Store_Y_Velocity
58194 CP 56 Jump to Handle_Carrying_Eagle_Check_Contact if the y velocity has reached 56.
58196 JR NC,Handle_Carrying_Eagle_Check_Contact
This entry point is used by the routine at Accelerate_Eagle_Up.
Handle_Carrying_Eagle_Store_Y_Velocity 58198 LD (IX+9),A Store the y velocity.
This entry point is used by the routine at Accelerate_Eagle_Up.
Check for contact with the decorations and the bubbles, and bounce off them.
Handle_Carrying_Eagle_Check_Contact 58201 PUSH DE Stash the flags of the room.
58202 CALL Check_Decoration_Contact Check for contact with the decorations.
58205 LD D,C Store the result in D.
58206 CALL Check_Bubble_Contact Check for contact with the bubbles.
58209 LD A,C Copy the result to A.
58210 OR D Combine it with the result for the decorations.
58211 LD C,A Store the combined result in C.
58212 POP DE Restore the flags of the room.
58213 BIT 2,C Jump to Handle_Carrying_Eagle_Move_X if the eagle is not touching anything.
58215 JR Z,Handle_Carrying_Eagle_Move_X
58217 BIT 1,C Jump to Handle_Carrying_Eagle_Check_Underside if the eagle is not on top of the object.
58219 JR Z,Handle_Carrying_Eagle_Check_Underside
58221 BIT 5,C Jump to Handle_Carrying_Eagle_Check_Sides if the object is a bubble and the eagle is away from the middle of it.
58223 JR NZ,Handle_Carrying_Eagle_Check_Sides
58225 LD A,(IX+9) Fetch the y velocity.
58228 AND A Jump to Handle_Carrying_Eagle_Move_X if the eagle is moving up already.
58229 JP M,Handle_Carrying_Eagle_Move_X
58232 CPL Invert the y velocity, to send the eagle up.
58233 LD (IX+9),A Store the y velocity.
58236 CALL Choose_Eagle_Target Choose a new target.
58239 JR Handle_Carrying_Eagle_Move_X Jump to Handle_Carrying_Eagle_Move_X.
Handle_Carrying_Eagle_Check_Underside 58241 BIT 0,C Jump to Handle_Carrying_Eagle_Check_Sides if the eagle is not near the middle of the object.
58243 JR NZ,Handle_Carrying_Eagle_Check_Sides
58245 LD A,(IX+9) Fetch the y velocity.
58248 AND A Jump to Handle_Carrying_Eagle_Check_Sides if the eagle is moving down already.
58249 JP P,Handle_Carrying_Eagle_Check_Sides
58252 CPL Invert the y velocity, to send the eagle down.
58253 LD (IX+9),A Store the y velocity.
Handle_Carrying_Eagle_Check_Sides 58256 LD A,(IX+8) Fetch the x velocity.
58259 BIT 7,C Jump to Handle_Carrying_Eagle_Bounce_Left if the eagle is not to the right of the object.
58261 JR Z,Handle_Carrying_Eagle_Bounce_Left
58263 AND A Jump to Handle_Carrying_Eagle_Move_X if the eagle is moving to the right already.
58264 JP P,Handle_Carrying_Eagle_Move_X
58267 CPL Invert the x velocity.
58268 LD (IX+8),A Store the x velocity.
58271 CALL Choose_Eagle_Target Choose a new target.
58274 JR Handle_Carrying_Eagle_Move_X Jump to Handle_Carrying_Eagle_Move_X.
Handle_Carrying_Eagle_Bounce_Left 58276 AND A Jump to Handle_Carrying_Eagle_Move_X if the eagle is moving to the left already.
58277 JP M,Handle_Carrying_Eagle_Move_X
58280 CPL Invert the x velocity.
58281 LD (IX+8),A Store the x velocity.
58284 CALL Choose_Eagle_Target Choose a new target.
Move the eagle horizontally.
Handle_Carrying_Eagle_Move_X 58287 LD A,(IX+11) Fetch the contact flags.
58290 AND %11101110 Reset bits 0 and 4 (the ceiling and the floor).
58292 LD (IX+11),A Store the contact flags.
58295 LD L,(IX+8) Fetch the x velocity into L.
58298 BIT 7,L Test the sign of the x velocity.
58300 LD H,0 Clear the high byte of the x velocity (as a word).
58302 JR Z,Handle_Carrying_Eagle_Set_Sabreman_Velocity Jump to Handle_Carrying_Eagle_Set_Sabreman_Velocity if the x velocity is positive.
58304 LD H,255 Set the high byte of the x velocity to 255 to extend the sign.
Handle_Carrying_Eagle_Set_Sabreman_Velocity 58306 LD A,L Copy the x velocity to A.
58307 SRA A Divide it by sixteen, keeping its sign.
58309 SRA A
58311 SRA A
58313 SRA A
58315 LD (36640),A Set the x velocity of Sabreman.
58318 CALL Move_Object_Horizontally Move the eagle horizontally (see Move_Object_Horizontally). The new x position is returned in A.
58321 JP Z,Limit_Eagle_Sideways_Movement Jump to Limit_Eagle_Sideways_Movement if the new x position is less than 128.
58324 CP 208 Jump to Handle_Carrying_Eagle_Store_X if the new x position is less than 208.
58326 JR C,Handle_Carrying_Eagle_Store_X
58328 BIT 2,E Jump to Limit_Eagle_Sideways_Movement_Right_Gap if the room has no wall on the right.
58330 JP Z,Limit_Eagle_Sideways_Movement_Right_Gap
58333 LD A,(IX+8) Fetch the x velocity.
58336 CPL Invert it.
58337 LD (IX+8),A Store the x velocity.
58340 CALL Choose_Eagle_Target Choose a new target.
58343 LD A,207 Set the x position to 207.
This entry point is used by the routine at Limit_Eagle_Sideways_Movement.
Handle_Carrying_Eagle_Store_X 58345 LD (IX+1),A Store the x position.
58348 LD A,(IX+11) Fetch the contact flags.
58351 AND %10111011 Reset bits 2 and 6 (the right and left walls).
58353 LD (IX+11),A Store the contact flags.
Move the eagle vertically.
58356 LD L,(IX+9) Fetch the y velocity into L.
58359 BIT 7,L Test the sign of the y velocity.
58361 LD H,0 Clear the high byte of the y velocity (as a word).
58363 JR Z,Handle_Carrying_Eagle_Move_Y Jump to Handle_Carrying_Eagle_Move_Y if the y velocity is positive.
58365 LD H,255 Set the high byte of the y velocity to 255 to extend the sign.
Handle_Carrying_Eagle_Move_Y 58367 CALL Move_Object_Vertically Move the eagle vertically (see Move_Object_Vertically). The new y position is returned in A.
58370 JP Z,Limit_Eagle_Vertical_Movement Jump to Limit_Eagle_Vertical_Movement if the new y position is less than 128.
58373 CP 159 Jump to Handle_Carrying_Eagle_Store_Y if the new y position is less than 159.
58375 JR C,Handle_Carrying_Eagle_Store_Y
58377 BIT 4,E Jump to Limit_Eagle_Vertical_Movement_Bottom_Gap if the room has no floor.
58379 JP Z,Limit_Eagle_Vertical_Movement_Bottom_Gap
58382 LD A,(IX+9) Fetch the y velocity.
58385 CPL Invert it.
58386 LD (IX+9),A Store the y velocity.
58389 CALL Choose_Eagle_Target Choose a new target.
58392 LD A,159 Set the y position to 159.
This entry point is used by the routine at Limit_Eagle_Vertical_Movement.
Handle_Carrying_Eagle_Store_Y 58394 LD (IX+3),A Store the y position.
58397 JP Update_Object_Sprite Jump to Update_Object_Sprite.
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