Bomb Massacre | Case File

Mission Brief

Build a 2D action platformer for the GMTK Game Jam around a high-risk 'cook-the-bomb' mechanic where blasts carve circular craters out of destructible tilemap geometry and eliminate enemies, extending Unity's 2D Platformer Microgame template under strict jam time constraints.

Key Systems Engineered

Single-Button Cook-to-Throw Bomb Loop & Fixed Pool of 3 (PlayerController.cs & BombHandler.cs)

Pressing the Bomb action dequeues a bomb from a pre-instantiated Queue<GameObject> pool of 3, parents it to bombCarryPosition, and switches its Rigidbody2D to Kinematic. While carried, maxHoldTimer increments each frame, growing explosionRadius in discrete +1f per-second steps from 1f up to 3f over a 5-second maxHoldTime while syncing the fuse sprite frame (FloorToInt(maxHoldTimer / (maxHoldTime / spriteCount))). Holding past 5s explodes the bomb in the player's hands; pressing Bomb again unparents and launches it along Vector2(facingDirection, 0.5f).normalized.

Circular Bounding-Grid Tilemap Crater Carving (DestroyTilesInRadius)

Converts the explosion's world-space center to Tilemap cell coordinates, iterates a bounding square of CeilToInt(radius) cells in each axis, converts each candidate cell back to world space, and clears only cells satisfying Vector2.Distance(center, cellWorldPos) <= radius — carving true circular craters out of a square grid alongside standalone 2-HP DestructibleBlock objects.

Single-Scene Spawn-Point Level Flow, Checkpoints & Tiled Pipeline

Authors levels externally in Tiled Map Editor (Bombs.tmx, BombsLevel1.tmx, BombsLevel2.tmx, BombsLevel2f.tmx) and switches levels within a single Unity scene by updating PlatformerModel.spawnPoint and scheduling a PlayerSpawn event via the template's Simulation queue, paired with trigger-based Checkpoint.cs actors.

Boss Fight: The Boss I Didn't Build (Scope Discipline) & Mid-Physics-Callback Safety

An elaborate end-of-game boss fight was part of the initial jam concept, but was deliberately cut mid-jam to prevent feature creep from compromising the core mechanic. Instead, that time went into polishing the 3-bomb pool, deferring collision explosions via an explodeNextFrame flag so tile destruction never executes mid-OnCollisionEnter2D physics callback, adding an explicit distance check so the player takes blast damage even if physics layer masks are misconfigured, and writing a procedural 64x64 Texture2D circle generator as a visual fallback.

Scope Discipline Note

Base Template: Unity 2D Platformer Microgame Template

Provided by Base:

Core player horizontal movement/jump physics, patrol-path EnemyController AI, the Simulation / HeapQueue / Fuzzy discrete-event scheduling framework, KinematicObject, ParallaxLayer, and AnimationController.

Engineered by Me:

The complete bomb pickup/cook/throw/explode system (BombHandler & PlayerController bomb logic), circular tilemap destruction algorithm (DestroyTilesInRadius), 2-HP cracked-sprite DestructibleBlock, Checkpoint respawn integration, single-scene LevelSelectMenu, procedural fallback explosion sprite generator, and all Tiled (.tmx) level designs.

Implementation Details

Architecture & Deep Dive

Bomb Massacre extends Unity’s 2D Platformer Microgame template with an original bomb mechanic designed under game jam time pressure. The core loop revolves around a cook-to-throw risk/reward system backed by a fixed pool of 3 bombs.

Bomb Mechanic

Picking up a bomb starts a hold timer that grows the explosion radius in discrete steps (1f → 2f → 3f over 5 seconds). Holding too long detonates the bomb in the player’s hands. The fuse sprite animates in sync with the timer via integer frame indexing.

Tilemap Destruction

The DestroyTilesInRadius algorithm converts world-space positions to tilemap cell coordinates, iterates a bounding square, and clears only cells within the circular radius — creating true circular craters in the square-grid tilemap. Explosions are deferred via an explodeNextFrame flag to avoid mutating tilemaps during physics callbacks.

Scope Discipline

The planned boss fight was deliberately cut mid-jam to focus on polishing the core mechanic, defensive fallbacks (procedural explosion sprites), and level design quality.

Controls

WASD / Arrow Keys: Move · Space: Jump · B: Pick Up / Throw Bomb · Esc: Pause

Loot & Rewards

Shipped a complete, playable WebGL build to itch.io before the GMTK Game Jam deadline with full source code on GitHub.
Includes defensive jam-time fallbacks: runtime procedural 64x64 circle sprite generation with coroutine fade-out when no VFX prefab is assigned, and [ContextMenu] editor test hooks on DestructibleBlock.