Platformer

Platformer

A playbook for 2D platformers — the run/jump controller "feel", level structure, hazards, and goals. This is a compositional skill: it wires an engine movement skill, a tilemap skill, and design skills into a working game. It does not re-teach physics or tilemaps; it tells you what to build and how to make jumping feel good.

When to use

• Use when building a side-scrolling or single-screen platformer, a "Mario-like" /

"Celeste-like", or any game whose core verb is jump between surfaces.

• Use when a jump feels floaty, unresponsive, or "unfair" and you need feel fixes

(coyote time, jump buffering, variable height, corner correction).

**When not to use:** top-down movement with no gravity → use the engine movement skill directly. 3D first-person traversal → fps-shooter. Grid/turn movement → roguelike. For the raw kinematic body API, use godot-2d-movement (or your engine's controller skill).

Core loop

Observe a gap/hazard → commit to a jump or move → land safely (or die) → reach the next checkpoint/goal. A platformer lives or dies on the moment-to-moment feel of that single jump, repeated thousands of times. Tighten the controller first; everything else is content.

Must-have systems

1. Run/jump controller — horizontal accel/decel, gravity, jump, with the feel aids below.
2. Solid + one-way collision — ground, walls, and "jump-through" platforms.
3. Level geometry — a tilemap or hand-placed colliders; the playable space.
4. Hazards + death/respawn — spikes, pits, enemies; reset to the last checkpoint.
5. Checkpoints / level goal — progress markers and a win condition (flag, door, exit).
6. Camera — follows the player with a deadzone and look-ahead, clamped to level bounds.
7. Juice — landing dust, squash/stretch, hit-stop, sound. Cheap, huge feel payoff.

Design knobs (make the jump feel right)

Tune these by outcome (height in tiles, time to apex in seconds), not by raw numbers.

| Knob | Effect | Sane starting point | |------|--------|---------------------| | Max jump height | reach | 3–4 tiles | | Time to apex | "weight"/snappiness | 0.30–0.40 s | | Fall gravity multiplier | snappy, non-floaty fall | 1.5–2.0× rise gravity | | Coyote time | jump just after leaving a ledge | 0.08–0.12 s (~5–7 frames @60) | | Jump buffer | press just before landing still jumps | 0.10–0.15 s | | Variable jump cut | tap = short hop, hold = full | cut upward velocity ×0.4–0.5 on release | | Apex hang | brief float at the top for air control | reduce gravity ×0.5 near |vy| 0 and coyotetimer > 0: velocity.y = jumpvelocity buffertimer = 0 coyotetimer = 0 # consume both so we can't double-jump

Variable height: releasing jump early while still rising cuts the arc short.

if jumpreleasedthis_frame and velocity.y 0 else gravity velocity.y += g * dt

### 3. One-way platforms

Solid from above, pass-through from below. Most engines expose a "one-way collision" flag on
the tile/collider; enable it and let the player **drop through** by disabling that collision
for a few frames when the player holds Down + Jump. Do not re-implement collision math.

## Pitfalls / failure modes

- **Per-frame movement not scaled by `dt`** → speed changes with frame rate. Every velocity
  integration and timer must use `dt`. (See `physics-tuning`.)
- **Floaty jumps** → symmetric gravity. Make fall gravity heavier than rise gravity.
- **"The jump didn't register"** → no input buffering. Buffer presses for ~0.1 s before landing.
- **"I fell off and couldn't jump"** → no coyote time. Allow a jump for ~0.1 s after leaving ground.
- **Sticking to walls / catching on tile seams** → use a single capsule/box collider, not
  per-tile colliders, and add corner correction.
- **Tunneling through floors at high speed** → enable continuous collision / smaller fixed
  timestep for fast bodies (see `physics-tuning`).
- **Camera snaps and induces nausea** → smooth/lerp the follow, add a deadzone, clamp to bounds.
- **Difficulty wall from bad teaching** → introduce one mechanic per area before combining them.

## Composition (build it from these skills)

- **Controller body:** `godot-2d-movement` (Godot `CharacterBody2D`); for other engines use
  the engine core + physics skill (`unity-physics`, `phaser-arcade-physics`, `pygame-core`).
- **Levels:** `godot-tilemap` / `unity-tilemap-2d` for geometry; `level-design` for layout,
  pacing, and teaching order.
- **Feel/physics:** `physics-tuning` for timestep, CCD, and stability.
- **Input:** `input-systems` for buffering, rebinding, and gamepad support.
- **Polish:** `audio-design` for SFX/music; the engine animation skill for squash/stretch.
- **Process:** `prototype-fast` to greybox the controller before building content.

## References

- For jump math derivation, a full feel-tuning table, corner correction, moving/one-way
  platforms, and camera follow, read `references/feel-tuning.md`.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [gamedev-skills](https://github.com/gamedev-skills)
- **Source:** [gamedev-skills/awesome-gamedev-agent-skills](https://github.com/gamedev-skills/awesome-gamedev-agent-skills)
- **License:** Apache-2.0

Install and usage instructions live in the source repository linked above.