oracle-of-secrets/Docs/Sprites/Enemies/Twinrova.md

Twinrova Boss Sprite Analysis

Overview

The twinrova sprite (ID: Sprite_Twinrova, which is $CE) is a complex, multi-phase boss designed to override the vanilla Blind and Blind Maiden sprites. It features a dramatic transformation from Blind Maiden into Twinrova, followed by alternating phases where Twinrova switches between Koume (fire) and Kotake (ice) forms, each possessing distinct attacks and environmental interactions.

Key Properties:

• Sprite ID: Sprite_Twinrova ($CE)
• Description: A multi-phase boss that transforms from Blind Maiden, then alternates between fire (Koume) and ice (Kotake) forms.
• Number of Tiles: 6
• Health: 00 (Health is managed by Sprite_Twinrova_CheckIfDead and phase transitions.)
• Damage: 00 (Damage dealt to Link is likely handled by its attacks.)
• Special Properties:
  • !Boss = 01 (Correctly identified as a boss.)
  • !Shadow = 01 (Draws a shadow.)
  • !Hitbox = 03
  • !CollisionLayer = 01 (Checks both layers for collision.)

Custom Variables/Macros:

• !AnimSpeed = 8: Defines the animation speed for various states.
• Twinrova_Front(), Twinrova_Back(), Twinrova_Ready(), Twinrova_Attack(), Show_Koume(), Show_Kotake(), Twinrova_Hurt(): Macros for playing specific animations, enhancing code readability.
• $AC: A RAM address used to store the current attack type (Fire or Ice).

Main Logic Flow (Sprite_Twinrova_Main):

The boss's behavior is governed by a detailed state machine:

• Twinrova_Init (0x00): Initial state. Displays an introductory message and transitions to Twinrova_MoveState.
• Twinrova_MoveState (0x01): The core movement and phase management state. It checks SprHealth, X to determine if Twinrova is in Phase 1 (single entity) or Phase 2 (alternating forms).
  • Phase 1: Twinrova moves around, randomly spawning Fire/Ice Keese, or preparing Fire/Ice attacks.
  • Phase 2: Twinrova alternates between Twinrova_KoumeMode (fire) and Twinrova_KotakeMode (ice) forms.
• Twinrova_MoveForwards (0x02), Twinrova_MoveBackwards (0x03): Handles movement using Sprite_FloatTowardPlayer and Sprite_CheckTileCollision.
• Twinrova_PrepareAttack (0x04): Prepares either a Fire or Ice attack based on the value in $AC.
• Twinrova_FireAttack (0x05): Executes a Fire attack. Restores floor tiles, uses JSL Sprite_Twinrova_FireAttack (a shared function for the actual attack), and randomly releases fireballs (ReleaseFireballs).
• Twinrova_IceAttack (0x06): Executes an Ice attack using JSL Sprite_Twinrova_IceAttack (a shared function).
• Twinrova_Hurt (0x07): Manages Twinrova taking damage. Plays a hurt animation and, after a timer, determines whether to dodge or retaliate with a fire or ice attack.
• Twinrova_KoumeMode (0x08): Koume (fire) form. Spawns pit hazards (AddPitHazard), falling tiles (Ganon_SpawnFallingTilesOverlord), and fireballs (Sprite_SpawnFireball). Uses RageModeMove for dynamic movement.
• Twinrova_KotakeMode (0x09): Kotake (ice) form. Can spawn lightning (JSL $1DE612) and uses RageModeMove for dynamic movement.
• Twinrova_Dead (0x0A): Handles Twinrova's death sequence, killing all spawned friends and playing a hurt animation.

Initialization (Sprite_Twinrova_Prep):

• Checks for the presence of the Blind Maiden ($7EF3CC = $06). If the Maiden is present, Twinrova is killed, indicating that Twinrova spawns from the Blind Maiden.
• Sets initial health to $5A (90 decimal).
• Configures deflection (SprDefl = $80), bump damage (SprBump = $04), and ensures Twinrova is not invincible.
• Configures Blind Boss startup parameters and initializes various timers and SprMisc variables.

Death Check (Sprite_Twinrova_CheckIfDead):

• Monitors SprHealth, X. If health is zero or negative, it triggers the boss's death sequence, setting SprState = $04 (kill sprite boss style) and SprAction = $0A (Twinrova_Dead stage).

Movement (RageModeMove, DoRandomStrafe, VelocityOffsets):

• RageModeMove: A sophisticated routine for dynamic, floaty movement. It randomly determines a movement mode (predictive movement towards player, random strafe, random dodge, stay in place) based on timers and probabilities. It also handles evasive actions.
• DoRandomStrafe: Generates random strafing movement.
• VelocityOffsets: A table defining X and Y speed offsets for movement.

Environmental Interactions (Twinrova_RestoreFloorTile, RestoreFloorTile, AddPitHazard, Ganon_SpawnFallingTilesOverlord):

• Twinrova_RestoreFloorTile / RestoreFloorTile: Restores floor tiles, likely after they have been modified by an attack.
• AddPitHazard: Adds a pit hazard to the floor.
• Ganon_SpawnFallingTilesOverlord: Spawns falling tiles (reused from Ganon's mechanics).

Drawing (Sprite_Twinrova_Draw):

• Uses standard OAM allocation routines.
• Handles complex animation frames, x/y offsets, character data, properties, and sizes for drawing Twinrova.
• Utilizes 16-bit operations for precise drawing calculations.

Graphics Transfer (ApplyTwinrovaGraphics):

• Handles DMA transfer of graphics data (twinrova.bin) to VRAM.

Attack Spawning (Fireball_Configure, ReleaseFireballs, Sprite_SpawnFireKeese, Sprite_SpawnIceKeese, JSL Sprite_SpawnFireball, JSL $1DE612 (Sprite_SpawnLightning)):

• Twinrova can spawn various projectiles and enemies, including fireballs, Fire Keese, Ice Keese, and lightning.

Blind Maiden Integration:

Twinrova's fight is deeply integrated with the Blind Maiden mechanics:

• Follower_BasicMover: This routine is hooked to check if the follower is the Blind Maiden, triggering the transformation to Twinrova.
• Follower_CheckBlindTrigger: Checks if the Blind Maiden follower is within a specific trigger area.
• Blind_SpawnFromMaiden: This is the core routine for the transformation. It applies Twinrova graphics, sets Twinrova's initial state and position based on the Maiden's, and sets various timers and properties.
• SpritePrep_Blind_PrepareBattle: This routine is overridden to handle Twinrova's prep or to despawn if a room flag is set.

Discrepancies/Notes:

• Health Management: The !Health property is 00. The boss's health is managed by Sprite_Twinrova_CheckIfDead and phase transitions.
• Code Reuse: There is extensive code reuse from other sprites/bosses (e.g., Sprite_Twinrova_FireAttack is also used by KydreeokHead, Ganon_SpawnFallingTilesOverlord in Koume mode, Sprite_SpawnFireKeese/Sprite_SpawnIceKeese in MoveState). This is an efficient practice but requires careful management to ensure thematic consistency and avoid unintended side effects.
• Hardcoded Addresses: Several JSL calls are to hardcoded addresses (e.g., JSL $1DE612 for lightning). These should ideally be replaced with named labels for better maintainability.
• Blind Maiden Overrides: The boss heavily relies on overriding vanilla Blind Maiden behavior, which is a common ROM hacking technique but requires careful understanding of the original game's code.
• TargetPositions: This table is defined but appears unused in the provided code.