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Add new sprite documentation for Minecart, Pedestal, Portal, and Switch Track

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- Created detailed documentation for the Minecart sprite, outlining its properties, constants, collision setup, main logic, and design patterns.
- Added documentation for the Pedestal sprite, including its vanilla overrides, custom logic for item interaction, and event triggering based on area context.
- Introduced documentation for the Portal sprite, detailing its two-way warping system, initialization, main logic, and helper routines for seamless transitions.
- Documented the Switch Track sprite, explaining its interactive behavior, state-based animation, and integration with external switches for dynamic track manipulation.
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# Booki Sprite Analysis
This document provides a detailed analysis of the `booki.asm` sprite, outlining its properties, core routines, and behavioral patterns.
## 1. Sprite Properties
The following `!SPRID` constants define Booki's fundamental characteristics:
```asm
!SPRID = Sprite_Booki
!NbrTiles = 02 ; Number of tiles used in a frame
!Harmless = 00 ; 00 = Sprite is Harmful, 01 = Sprite is Harmless
!HVelocity = 00 ; Is your sprite going super fast? put 01 if it is
!Health = 00 ; Number of Health the sprite have (dynamically set in _Prep)
!Damage = 00 ; (08 is a whole heart), 04 is half heart
!DeathAnimation = 00 ; 00 = normal death, 01 = no death animation
!ImperviousAll = 00 ; 00 = Can be attack, 01 = attack will clink on it
!SmallShadow = 00 ; 01 = small shadow, 00 = no shadow
!Shadow = 00 ; 00 = don't draw shadow, 01 = draw a shadow
!Palette = 00 ; Unused in this template (can be 0 to 7)
!Hitbox = 00 ; 00 to 31, can be viewed in sprite draw tool
!Persist = 00 ; 01 = your sprite continue to live offscreen
!Statis = 00 ; 00 = is sprite is alive?, (kill all enemies room)
!CollisionLayer = 00 ; 01 = will check both layer for collision
!CanFall = 00 ; 01 sprite can fall in hole, 01 = can't fall
!DeflectArrow = 00 ; 01 = deflect arrows
!WaterSprite = 00 ; 01 = can only walk shallow water
!Blockable = 00 ; 01 = can be blocked by link's shield?
!Prize = 00 ; 00-15 = the prize pack the sprite will drop from
!Sound = 00 ; 01 = Play different sound when taking damage
!Interaction = 00 ; ?? No documentation
!Statue = 00 ; 01 = Sprite is statue
!DeflectProjectiles = 00 ; 01 = Sprite will deflect ALL projectiles
!ImperviousArrow = 00 ; 01 = Impervious to arrows
!ImpervSwordHammer = 00 ; 01 = Impervious to sword and hammer attacks
!Boss = 00 ; 00 = normal sprite, 01 = sprite is a boss
```
**Note:** `!Health` and `!Damage` are initially set to `00` but are dynamically determined during initialization.
## 2. Core Routines
### 2.1. `Sprite_Booki_Long` (Main Loop)
This is the primary entry point for Booki's per-frame execution, called by the game engine. It handles drawing, shadow rendering, and then dispatches to the main logic routine if the sprite is active.
```asm
Sprite_Booki_Long:
{
PHB : PHK : PLB ; Set up bank registers
JSR Sprite_Booki_Draw ; Call drawing routine
JSL Sprite_DrawShadow ; Draw a shadow (if !Shadow is 01)
JSL Sprite_CheckActive : BCC .SpriteIsNotActive ; Check if sprite is active
JSR Sprite_Booki_Main ; If active, run main logic
.SpriteIsNotActive
PLB ; Restore bank register
RTL ; Return from long routine
}
```
### 2.2. `Sprite_Booki_Prep` (Initialization)
This routine is executed once when Booki is first spawned. It dynamically sets Booki's health based on Link's current sword level and initializes `SprMiscB`.
```asm
Sprite_Booki_Prep:
{
PHB : PHK : PLB
LDA.l Sword : DEC A : TAY ; Get Link's sword level (0-3), adjust to 0-indexed
LDA.w .health, Y : STA.w SprHealth, X ; Set health based on sword level
STZ.w SprMiscB, X ; Initialize SprMiscB to 0
PLB
RTL
.health ; Health values for each sword level
db $04, $08, $10, $18 ; 4, 8, 16, 24 HP
}
```
### 2.3. `Sprite_Booki_Main` (Behavioral State Machine)
This routine manages Booki's AI through a state machine, using `SprAction, X` to determine the current behavior. It utilizes `JumpTableLocal` for efficient state transitions.
```asm
Sprite_Booki_Main:
{
LDA.w SprAction, X
JSL JumpTableLocal ; Jump to the routine specified by SprAction
dw StalkPlayer ; State 0
dw HideFromPlayer ; State 1
dw HiddenFromPlayer ; State 2
dw ApproachPlayer ; State 3
StalkPlayer:
{
%PlayAnimation(0,1,16) ; Animate frames 0-1 every 16 frames
JSR Sprite_Booki_Move ; Handle movement
RTS
}
HideFromPlayer:
{
%PlayAnimation(0,4,16) ; Animate frames 0-4 every 16 frames
LDA.w SprTimerA, X : BNE + ; Check timer
INC.w SprAction, X ; If timer is 0, transition to HiddenFromPlayer
+
RTS
}
HiddenFromPlayer:
{
%PlayAnimation(4,4,16) ; Animate frame 4 every 16 frames (static)
JSR Sprite_Booki_Move ; Handle movement
JSL GetRandomInt : AND.b #$03 : BEQ + ; Random chance to transition
INC.w SprAction, X ; If random condition met, transition to ApproachPlayer
+
RTS
}
ApproachPlayer:
{
%PlayAnimation(5,9,16) ; Animate frames 5-9 every 16 frames
JSR Sprite_Booki_Move ; Handle movement
RTS
}
}
```
### 2.4. `Sprite_Booki_Move` (Movement and Interaction Logic)
This routine is called by the various states in `Sprite_Booki_Main` to handle Booki's physical interactions and movement. It also manages Booki's "float" behavior (`SlowFloat` or `FloatAway`) based on `SprMiscB`.
```asm
Sprite_Booki_Move:
{
JSL Sprite_Move ; Apply velocity
JSL Sprite_BounceFromTileCollision ; Handle collision with tiles
JSL Sprite_PlayerCantPassThrough ; Prevent player from passing through Booki
JSL Sprite_DamageFlash_Long ; Handle damage flashing
JSL Sprite_CheckIfRecoiling ; Check for recoil state
JSL Sprite_IsToRightOfPlayer : CPY.b #$01 : BNE .ToRight ; Determine if Booki is to the right of Link
LDA.b #$01 : STA.w SprMiscC, X ; Set SprMiscC to 1 (for horizontal flip)
JMP .Continue
.ToRight
STZ.w SprMiscC, X ; Set SprMiscC to 0 (no flip)
.Continue
JSL Sprite_CheckDamageToPlayer ; Check if Booki damages Link
JSL Sprite_CheckDamageFromPlayer : BCC .no_damage ; Check if Link damages Booki
LDA.b #$01 : STA.w SprMiscB, X ; If damaged, set SprMiscB to 1 (FloatAway state)
.no_damage
LDA.w SprMiscB, X
JSL JumpTableLocal ; Jump to movement routine based on SprMiscB
dw SlowFloat ; SprMiscB = 0
dw FloatAway ; SprMiscB = 1
SlowFloat:
{
LDY #$04
JSL GetRandomInt : AND.b #$04 ; Introduce some randomness to movement
JSL Sprite_FloatTowardPlayer ; Float towards Link
PHX
JSL Sprite_DirectionToFacePlayer ; Update facing direction
; Check if too close to player
LDA.b $0E : CMP.b #$1A : BCS .NotTooClose
LDA.b $0F : CMP.b #$1A : BCS .NotTooClose
LDA.b #$01 : STA.w SprMiscB, X ; If too close, switch to FloatAway
LDA.b #$20 : STA.w SprTimerA, X ; Set timer
%GotoAction(1) ; Transition to HideFromPlayer state
.NotTooClose
PLX
RTS
}
FloatAway:
{
JSL GetRandomInt : AND.b #$04 ; Introduce some randomness to movement
JSL Sprite_FloatAwayFromPlayer ; Float away from Link
PHX
JSL Sprite_DirectionToFacePlayer ; Update facing direction
; Check if far enough from player
LDA.b $0E : CMP.b #$1B : BCC .NotTooClose
LDA.b #$1B : CMP.b $0F : BCC .NotTooClose ; Corrected comparison for $0F
LDA.b #$00 : STA.w SprMiscB, X ; If far enough, switch to SlowFloat
%GotoAction(0) ; Transition to StalkPlayer state
.NotTooClose
PLX
RTS
}
}
```
### 2.5. `Sprite_Booki_Draw` (Drawing Routine)
This routine is responsible for rendering Booki's graphics. It uses a custom OAM (Object Attribute Memory) allocation and manipulation logic rather than the `%DrawSprite()` macro. It dynamically determines the animation frame and applies horizontal flipping based on `SprMiscC`.
```asm
Sprite_Booki_Draw:
{
JSL Sprite_PrepOamCoord ; Prepare OAM coordinates
JSL Sprite_OAM_AllocateDeferToPlayer ; Allocate OAM slots, deferring to player
LDA.w SprGfx, X : CLC : ADC.w SprFrame, X : TAY ; Calculate animation frame index
LDA .start_index, Y : STA $06 ; Store start index for tiles
LDA.w SprFlash, X : STA $08 ; Store flash status
LDA.w SprMiscC, X : STA $09 ; Store horizontal flip status (0 or 1)
PHX
LDX .nbr_of_tiles, Y ; Load number of tiles for current frame (minus 1)
LDY.b #$00 ; Initialize Y for OAM buffer offset
.nextTile
PHX ; Save current Tile Index
TXA : CLC : ADC $06 ; Add Animation Index Offset
PHA ; Keep the value with animation index offset
ASL A : TAX ; Multiply by 2 for word access
REP #$20 ; Set A to 16-bit mode
LDA $00 : STA ($90), Y ; Store Y-coordinate
AND.w #$0100 : STA $0E ; Check if Y-coord is off-screen (high bit)
INY
LDA $02 : STA ($90), Y ; Store X-coordinate
CLC : ADC #$0010 : CMP.w #$0100 ; Check if X-coord is off-screen
SEP #$20 ; Set A to 8-bit mode
BCC .on_screen_y ; If on screen, continue
LDA.b #$F0 : STA ($90), Y ; If off-screen, move sprite off-screen
STA $0E
.on_screen_y
PLX ; Restore Tile Index
INY
LDA .chr, X : STA ($90), Y ; Store character (tile) number
INY
LDA.b $09 : BEQ .ToRight ; Check SprMiscC for horizontal flip
LDA.b #$29 : JMP .Prop ; If 1, use properties for flipped
.ToRight
LDA.b #$69 ; If 0, use properties for normal
.Prop
ORA $08 : STA ($90), Y ; Apply flash and store OAM properties
PHY
TYA : LSR #2 : TAY ; Calculate OAM buffer index for size
LDA.b #$02 : ORA $0F : STA ($92), Y ; Store size (16x16) in OAM buffer
PLY : INY
PLX : DEX : BPL .nextTile ; Loop for next tile
PLX ; Restore X (sprite index)
RTS
; =========================================================
; OAM Data Tables
.start_index
db $00, $01, $02, $03, $04, $05, $06, $07, $08, $09
.nbr_of_tiles
db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; All frames use 1 tile (0-indexed)
.chr
db $0E, $0C, $0A, $2C, $2E, $2E, $0A, $2C, $0C, $0E ; Tile numbers for each frame
}
```
## 3. Key Behaviors and Implementation Details
* **Dynamic Health:** Booki's health is not a fixed property but is determined at spawn time based on Link's current sword level. This allows for dynamic difficulty scaling.
* **State Management:** Booki employs a robust state machine using `SprAction, X` and `JumpTableLocal` to manage its behaviors: `StalkPlayer`, `HideFromPlayer`, `HiddenFromPlayer`, and `ApproachPlayer`. Transitions between these states are triggered by timers, random chance, or player proximity.
* **Player Interaction:**
* **Stalking/Approaching:** Booki uses `Sprite_FloatTowardPlayer` to move towards Link.
* **Hiding/Floating Away:** Booki uses `Sprite_FloatAwayFromPlayer` to retreat from Link, often triggered by taking damage or getting too close.
* **Damage:** Booki can damage Link on contact (`Sprite_CheckDamageToPlayer`) and reacts to damage from Link by transitioning to a `FloatAway` state.
* **Directional Facing:** `SprMiscC, X` is used as a flag to control horizontal flipping in the drawing routine, ensuring Booki always faces Link.
* **Custom OAM Drawing:** Unlike many sprites that might use the `%DrawSprite()` macro, Booki implements its OAM drawing logic directly. This provides fine-grained control over its appearance, including dynamic tile selection and horizontal flipping. The `REP #$20` and `SEP #$20` instructions are used to temporarily switch the accumulator to 16-bit mode for coordinate calculations, demonstrating careful management of the Processor Status Register.
* **Randomness:** `GetRandomInt` is used to introduce variability in Booki's movement patterns and state transitions, making its behavior less predictable.
* **`SprMiscB` Usage:** This variable acts as a sub-state for movement, toggling between `SlowFloat` (approaching) and `FloatAway` (retreating) behaviors.
* **`SprTimerA` Usage:** Used in the `HideFromPlayer` state to control how long Booki remains in that state before transitioning.
* **`Sprite_PlayerCantPassThrough`:** Ensures Booki acts as a solid object that Link cannot simply walk through.