gamemaker gml

GameMaker GML Rules

Code Organization

• Keep object event code short and move reusable behavior into scripts or functions.
• Use clear prefixes or naming conventions for scripts, objects, sprites, rooms, and globals.
• Prefer functions over copy-pasted event blocks.
• Keep create-step-draw responsibilities separate.
• Put initialization in Create, simulation in Step, and rendering-only work in Draw.

GML Style

• Use descriptive variable names and avoid one-letter names outside small loops.
• Prefer local variables with var or function-scoped declarations over unnecessary instance variables.
• Use constants, enums, and macros for repeated identifiers, layer names, states, and collision groups.
• Guard optional instance references with instance_exists.
• Keep global state minimal and document it.

Gameplay Architecture

• Use finite state machines for player, enemy, UI, and game-flow states.
• Keep collision logic explicit and deterministic.
• Separate input collection from action execution.
• Use alarms, timelines, or explicit timers consistently; do not mix patterns without reason.
• Store save data through structured maps/structs and version the save format.

Performance

• Avoid expensive searches such as broad instance_find or repeated collision scans in every Step event.
• Cache frequently used asset IDs, layer IDs, and object references when safe.
• Destroy data structures when no longer needed.
• Use object pooling for frequent projectiles, particles, or short-lived effects when allocation becomes costly.
• Profile before optimizing and keep hot-path code simple.

Debugging and Testing

• Add debug overlays for collision boxes, state, velocity, and AI decisions when useful.
• Use assertions or explicit guard clauses for impossible states.
• Test room transitions, pause/resume, save/load, and controller/keyboard input separately.
• Keep reproducible test rooms for complex mechanics.

Common Mistakes

• Do not put game logic in Draw events.
• Do not create data structures without destroying them.
• Do not rely on room editor instance order for critical behavior.
• Do not hardcode magic numeric state IDs.