Evil doll axe

Entity data
Entity pointer	$81:B592

An evil doll axe is an entity that is created by an evil doll whenever it throws an axe.

Behavior

The axe moves at a velocity of 4 times the given input velocity per frame. In the base game, the input velocities are either 0, 1, or -1 on each axis, so it will move at a rate of 4 pixels per frame on each axis.

Axes start with 2 HP and will be instantly destroyed when they run out of health. However, axes only take damage from sprite types 7 and 8, which are a wall breaking from player punching it as a monster, and an unused type respectively. Axes will also be destroyed if they touch a background tile that is solid to weapons or if they go off screen in multiplayer. The off-screen condition does not apply in single player; they will continue to travel until they hit a solid tile or reach the edge of the level.

Animation

The axe animation has 4 different animation frames and there are 6 frames of time between each. The animation is supposed to differ slightly based on which direction the axe is moving, but there are two bugs in the implementation for this:

1. Negative directions (up and left) are incorrectly mapped to the corresponding positive direction because the code only checks for the velocities being exactly equal to -1, but they have already been multiplied by 2 when this is checked.
2. The "down" direction is incorrectly mapped to "right"

The result of these two bugs is that all orthogonal directions are mapped to the animation for "right", and all diagonal directions are mapped to the animation for "down-right". For orthogonal directions, this doesn't matter since they all share the same animation anyway. However, the down-left and up-left animations supposed to show the axe rotating counter-clockwise, but don't.

RAM map

Entity arguments

Address	Length	Type	Description
$00	2	int16	X position
$02	2	int16	Y position
$04	2	int16	X velocity
$06	2	int16	Y velocity

Entity memory

Address	Length	Type	Description
$08	2	pointer16	Pointer to sprite
$0A	2	boolean	Axe has been destroyed
$0C	2	int16 0-based	Health
$0E	2	pointer16	Pointer to current state subroutine (always $B5B0)
$10	2	int16	Number of frames until next animation frame
$12	2	int16 0-based	Number of frames per animation frame (always 5)
$14	2	uint16	Current animation frame
$16	2	enum	Animation direction
$18	2	int16	X position
$1A	2	unused	Unused
$1C	2	int16	Y position
$1E	2	sprite type	Type of sprite collided with
$20	2	int16 /2	X velocity
$22	2	int16 /2	Y velocity
$24	2	pointer16	Pointer to animation table (always $ADDE)

Animation Directions

Value	Direction	Bugged direction
0x00	Up	Down
0x04	Up-right	Down-right
0x08	Right	Down
0x0C	Down-right
0x10	Down
0x14	Down-left	Down-right
0x18	Left	Down
0x1C	Up-left	Down-right
0x20	None