aede7551a3
- 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.
222 lines
7.1 KiB
Markdown
222 lines
7.1 KiB
Markdown
# Sea Urchin Sprite Analysis
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This document provides a detailed analysis of the `sea_urchin.asm` sprite, outlining its properties, core routines, and behavioral patterns.
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## 1. Sprite Properties
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The following `!SPRID` constants define Sea Urchin's fundamental characteristics:
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```asm
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!SPRID = Sprite_SeaUrchin
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!NbrTiles = 04 ; Number of tiles used in a frame
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!Harmless = 00 ; 00 = Sprite is Harmful, 01 = Sprite is Harmless
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!HVelocity = 00 ; Is your sprite going super fast? put 01 if it is
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!Health = 06 ; Number of Health the sprite have
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!Damage = 04 ; (08 is a whole heart), 04 is half heart
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!DeathAnimation = 00 ; 00 = normal death, 01 = no death animation
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!ImperviousAll = 00 ; 00 = Can be attack, 01 = attack will clink on it
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!SmallShadow = 00 ; 01 = small shadow, 00 = no shadow
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!Shadow = 01 ; 00 = don't draw shadow, 01 = draw a shadow
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!Palette = 00 ; Unused in this template (can be 0 to 7)
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!Hitbox = 00 ; 00 to 31, can be viewed in sprite draw tool
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!Persist = 00 ; 01 = your sprite continue to live offscreen
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!Statis = 00 ; 00 = is sprite is alive?, (kill all enemies room)
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!CollisionLayer = 00 ; 01 = will check both layer for collision
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!CanFall = 00 ; 01 sprite can fall in hole, 01 = can't fall
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!DeflectArrow = 00 ; 01 = deflect arrows
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!WaterSprite = 00 ; 01 = can only walk shallow water
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!Blockable = 01 ; 01 = can be blocked by link's shield?
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!Prize = 03 ; 00-15 = the prize pack the sprite will drop from
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!Sound = 00 ; 01 = Play different sound when taking damage
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!Interaction = 00 ; ?? No documentation
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!Statue = 00 ; 01 = Sprite is statue
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!DeflectProjectiles = 00 ; 01 = Sprite will deflect ALL projectiles
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!ImperviousArrow = 00 ; 01 = Impervious to arrows
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!ImpervSwordHammer = 00 ; 01 = Impervious to sword and hammer attacks
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!Boss = 00 ; 00 = normal sprite, 01 = sprite is a boss
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```
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**Note:** `!Health` is fixed at `06` and `!Damage` is `04` (half a heart).
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## 2. Core Routines
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### 2.1. `Sprite_SeaUrchin_Long` (Main Loop)
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This is the primary entry point for Sea Urchin's per-frame execution. It handles drawing, shadow rendering, and then dispatches to the main logic routine if the sprite is active.
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```asm
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Sprite_SeaUrchin_Long:
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{
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PHB : PHK : PLB
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JSR Sprite_SeaUrchin_Draw
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JSL Sprite_DrawShadow
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JSL Sprite_CheckActive : BCC .SpriteIsNotActive
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JSR Sprite_SeaUrchin_Main
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.SpriteIsNotActive
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PLB
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RTL
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}
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```
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### 2.2. `Sprite_SeaUrchin_Prep` (Initialization)
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This routine is executed once when Sea Urchin is first spawned. It sets the initial prize and conditionally modifies its imperviousness and prize based on the `WORLDFLAG` (likely for different game states or areas, such as the Eon Sea).
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```asm
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Sprite_SeaUrchin_Prep:
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{
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PHB : PHK : PLB
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LDA #$01 : STA.w SprPrize, X ; Default prize
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LDA.w WORLDFLAG : BEQ + ; Check WORLDFLAG
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; Eon Sea Urchin impervious to sword
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LDA.b #%10000100 : STA.w SprDefl, X ; Set imperviousness flags
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LDA.b #$07 : STA.w SprPrize, X ; Change prize for Eon Sea
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+
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PLB
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RTL
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}
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```
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### 2.3. `Sprite_SeaUrchin_Main` (Behavioral State Machine)
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This routine manages Sea Urchin's AI through a simple state machine, using `SprAction, X` to determine its current behavior. It includes `Idle` and `Death` states.
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```asm
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Sprite_SeaUrchin_Main:
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{
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LDA.w SprAction, X
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JSL JumpTableLocal
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dw Idle
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dw Death
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Idle:
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{
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%PlayAnimation(0,3,8)
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%PlayerCantPassThrough()
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%DoDamageToPlayerSameLayerOnContact()
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JSL Sprite_CheckDamageFromPlayer : BCC .NoDamage
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%GotoAction(1) ; Transition to Death state if damaged
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.NoDamage
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RTS
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}
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Death:
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{
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LDA.b #$06 : STA.w SprState, X ; Set sprite state to despawn
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LDA.b #$0A : STA.w SprTimerA, X
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STZ.w SprPrize,X
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JSL ForcePrizeDrop_long ; Force prize drop
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LDA.b #$09 : JSL SpriteSFX_QueueSFX3WithPan ; Play sound effect
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RTS
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}
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}
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```
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### 2.4. `Sprite_SeaUrchin_Draw` (Drawing Routine)
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This routine is responsible for rendering Sea Urchin's graphics. It uses a custom OAM allocation and manipulation logic to handle its multi-tile appearance and animation.
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```asm
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Sprite_SeaUrchin_Draw:
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{
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JSL Sprite_PrepOamCoord
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JSL Sprite_OAM_AllocateDeferToPlayer
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LDA $0DC0, X : CLC : ADC $0D90, X : TAY;Animation Frame
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LDA .start_index, Y : STA $06
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PHX
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LDX .nbr_of_tiles, Y ;amount of tiles -1
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LDY.b #$00
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.nextTile
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PHX ; Save current Tile Index?
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TXA : CLC : ADC $06 ; Add Animation Index Offset
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PHA ; Keep the value with animation index offset?
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ASL A : TAX
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REP #$20
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LDA $00 : CLC : ADC .x_offsets, X : STA ($90), Y
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AND.w #$0100 : STA $0E
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INY
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LDA $02 : CLC : ADC .y_offsets, X : STA ($90), Y
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CLC : ADC #$0010 : CMP.w #$0100
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SEP #$20
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BCC .on_screen_y
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LDA.b #$F0 : STA ($90), Y ;Put the sprite out of the way
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STA $0E
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.on_screen_y
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PLX ; Pullback Animation Index Offset (without the *2 not 16bit anymore)
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INY
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LDA .chr, X : STA ($90), Y
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INY
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LDA .properties, X : STA ($90), Y
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PHY
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TYA : LSR #2 : TAY
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LDA.b #$02 : ORA $0F : STA ($92), Y ; store size in oam buffer
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PLY : INY
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PLX : DEX : BPL .nextTile
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PLX
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RTS
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.start_index
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db $00, $01, $02, $03, $04, $05, $06, $07
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.nbr_of_tiles
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db 0, 0, 0, 0, 0, 0, 0, 0
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.x_offsets
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dw 0
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dw 0
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dw 0
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dw 0
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dw 0
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dw 0
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dw 0
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dw 0
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.y_offsets
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dw 0
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dw -1
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dw 0
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dw -1
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dw 0
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dw -1
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dw 0
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dw -1
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.chr
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db $EA
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db $EC
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db $EA
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db $EC
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db $EA
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db $EC
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db $EA
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db $EC
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.properties
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db $29
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db $29
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db $69
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db $69
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db $29
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db $29
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db $69
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db $69
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}
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```
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## 3. Key Behaviors and Implementation Details
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* **Fixed Health:** Sea Urchin has a fixed health of `06` and its health is not dynamically scaled based on Link's sword level.
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* **Dynamic Prize Drop and Imperviousness:** A notable feature is its conditional behavior based on the `WORLDFLAG`. If this flag is set (e.g., indicating a specific game area like the Eon Sea), the Sea Urchin becomes impervious to sword attacks (`SprDefl`) and drops a different prize. This demonstrates how global game state variables can influence individual sprite properties.
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* **State Management:** Sea Urchin uses a simple state machine with `Idle` and `Death` states, managed by `SprAction, X` and `JumpTableLocal`.
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* **Movement Patterns:** The Sea Urchin has a simple idle animation (`%PlayAnimation(0,3,8)`) and does not exhibit complex movement behaviors. It remains stationary but can be pushed by Link (`%PlayerCantPassThrough()`).
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* **Damage Handling:** Upon taking damage from Link (`Sprite_CheckDamageFromPlayer`), the Sea Urchin transitions to its `Death` state. In this state, it despawns (`STZ.w SprState, X`), forces a prize drop (`ForcePrizeDrop_long`), and plays a sound effect (`SpriteSFX_QueueSFX3WithPan`).
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* **Custom OAM Drawing:** Sea Urchin utilizes a custom OAM drawing routine to render its multi-tile appearance and animation. The drawing logic includes coordinate calculations with `REP`/`SEP` for 16-bit operations.
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