oracle-of-secrets/Docs/Sprites/Bosses/KydrogBoss.md

Kydrog Boss Sprite Analysis

Overview

The kydrog_boss sprite (ID: Sprite_KydrogBoss, which is $CB) represents the main Kydrog boss. This boss features multiple phases, dynamic movement, and the ability to summon stalfos offspring. It's a complex encounter designed to challenge the player through varied attack patterns and phase transitions.

Key Properties:

• Sprite ID: Sprite_KydrogBoss ($CB)
• Description: The main Kydrog boss, controlling its own movement, phases, and spawning stalfos offspring.
• Number of Tiles: 11
• Health: 00 (The boss's health is managed through CheckForNextPhase and Sprite_KydrogBoss_CheckIfDead, not directly by this property.)
• Damage: 00 (Damage dealt to Link is likely handled by its attacks or spawned offspring.)
• Special Properties:
  • !Boss = $01 (Correctly identified as a boss.)
  • !Shadow = 01 (Draws a shadow.)
  • !Hitbox = 03

Custom Variables:

• !ConsecutiveHits = $AC: Tracks consecutive hits on the boss, influencing its behavior.
• !KydrogPhase = $7A: Manages the current phase of the boss fight.
• !WalkSpeed = 10: Defines the boss's walking speed.

Main States/Actions (Sprite_KydrogBoss_Main Jump Table):

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

• KydrogBoss_Init (0x00): Initial state, plays an "Arms Crossed" animation, and transitions to KydrogBoss_WalkState after an intro timer.
• KydrogBoss_WalkState (0x01): The primary walking state. Manages phase transitions, handles damage, taunting, and determines the next walking direction (forward, backward, left, right) based on Link's position and proximity.
• KydrogBoss_WalkForward (0x02), KydrogBoss_WalkLeft (0x03), KydrogBoss_WalkRight (0x04), KydrogBoss_WalkBackward (0x05): These states handle movement in specific directions, playing corresponding animations and executing core movement logic.
• KydrogBoss_TakeDamage (0x06): Manages the boss taking damage. Increments !ConsecutiveHits, plays a damage animation, spawns stalfos offspring, and can trigger an ascend action.
• KydrogBoss_TauntPlayer (0x07): Plays a taunting animation, handles damage, and transitions to KydrogBoss_SummonStalfos.
• KydrogBoss_SummonStalfos (0x08): Plays a summoning animation, handles damage, spawns stalfos offspring, and can throw a bone projectile at Link.
• KydrogBoss_Death (0x09): Handles the boss's death sequence, including killing spawned friends, playing a flickering animation, and despawning.
• KydrogBoss_Ascend (0x0A): The boss ascends off-screen, increasing its SprHeight and spawning stalfos offspring. Transitions to KydrogBoss_Descend.
• KydrogBoss_Descend (0x0B): The boss descends, tracking Link's position, decreasing its SprHeight, and spawning stalfos offspring. Transitions back to KydrogBoss_WalkState.
• KydrogBoss_Abscond (0x0C): The boss moves away from Link, increasing its speed, and transitions back to KydrogBoss_WalkState.

Initialization (Sprite_KydrogBoss_Prep):

• Initializes !KydrogPhase to 00.
• Sets initial health to $A0 (160 decimal).
• Configures deflection (SprDefl), hitbox (SprHitbox), and bump damage (SprBump).
• Sets SprGfxProps to not invincible.
• Calls JSR KydrogBoss_Set_Damage to define its damage vulnerabilities.
• Sets initial sprite speeds and !Harmless = 00.
• Sets an intro timer (SprTimerD = $80).

Death Check (Sprite_KydrogBoss_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 = $09 (KydrogBoss_Death stage).

Phase Management (CheckForNextPhase):

This routine dynamically manages the boss's phases based on its current health:

• Phase One (!KydrogPhase = $00): Transitions to Phase Two when health drops below $20.
• Phase Two (!KydrogPhase = $01): Transitions to Phase Three when health drops below $20. Resets health to $80, sets action to KydrogBoss_WalkState, and increments SprFlash, X.
• Phase Three (!KydrogPhase = $02): Transitions to Phase Four when health drops below $20. Resets health to $80, sets action to KydrogBoss_WalkState.
• Phase Four (!KydrogPhase = $03): Sets action to KydrogBoss_WalkState.

Damage Table (KydrogBoss_Set_Damage):

• Defines how KydrogBoss reacts to various attack types (Boomerang, Sword, Arrow, Bomb, etc.), stored in a damage properties table.

Offspring Spawning (RandomStalfosOffspring, Sprite_Offspring_Spawn, Sprite_Offspring_SpawnHead):

• RandomStalfosOffspring: Randomly spawns either a normal stalfos offspring (Sprite_Offspring_Spawn) or a stalfos head offspring (Sprite_Offspring_SpawnHead), with a limit of 4 active stalfos.
• Sprite_Offspring_Spawn: Spawns a stalfos offspring (Sprite ID $A7 or $85).
• Sprite_Offspring_SpawnHead: Spawns a stalfos head offspring (Sprite ID $7C or $02).

Attacks (Kydrog_ThrowBoneAtPlayer):

• Kydrog_ThrowBoneAtPlayer: Spawns a bone projectile (Sprite ID $A7) that moves towards Link.

Movement (KydrogBoss_DoMovement, BounceBasedOnPhase):

• KydrogBoss_DoMovement: Handles damage checks, applies damage to Link on contact, flashes when damaged, and incorporates phase-based bouncing and stalfos spawning.
• BounceBasedOnPhase: Adjusts the boss's bounce speed based on the current !KydrogPhase.

Drawing (Sprite_KydrogBoss_Draw):

• Uses standard OAM allocation routines.
• Handles complex animation frames, x/y offsets, character data, properties, and sizes for drawing the boss.
• Utilizes 16-bit operations (REP #$30, SEP #$30) for precise drawing calculations.

Other Routines:

• StopIfTooClose() macro: Prevents the boss from getting too close to Link.
• Sprite_CheckIfFrozen: Checks if the sprite is frozen and unfreezes it after a timer.
• GetNumberSpawnStalfos: Counts the number of active stalfos offspring.
• SpawnSplash: Spawns a splash effect.
• SpawnBossPoof: Spawns a boss poof effect.
• HandleMovingSplash: Handles splash effects during movement.
• SpawnMedallion / SpawnMedallionAlt: Spawns a medallion.

Discrepancies/Notes:

• The main boss's health is intricately managed through SprHealth, X and !KydrogPhase, requiring a clear understanding of their interplay.
• The stalfos offspring are spawned using specific sprite IDs, which should be cross-referenced for full understanding.
• Many hardcoded values for timers, speeds, and offsets could be replaced with named constants for improved readability and maintainability.
• The code includes direct calls to sound effect functions (JSL $0DBB8A) and a commented-out call to JSL $01F3EC (Light Torch), which might be a leftover or an unimplemented feature.

Hardcoded Activation Trigger:

• As noted by the user, the activation trigger for KydrogBoss is hardcoded. Specifically, in the WaitForPlayerToApproach routine, the boss checks LDA.b $20 : CMP #$08C8. $20 represents Link's Y position, and $08C8 is a hardcoded Y-coordinate. This means the boss will only activate when Link reaches this specific Y-coordinate, making it difficult to relocate the boss to other overworld maps without modifying this value.