# Sandbox, values, and diagnostics [Back to JavaScript](https://rustic-game-engine.pages.dev/markdown/scripting/javascript.md). JavaScript cannot obtain another behavior's VM object. API 1.1 adds shared `Events.on`, `once`, `emit`, and object signals; see [Shared gameplay actions](https://rustic-game-engine.pages.dev/markdown/guides/gameplay-actions.md). There is no DOM, `window`, Node `require`, module loader, filesystem, network, environment, native browser timers, process, or editor/backend access. Use the engine-owned `Timer` facade for delayed/repeating gameplay callbacks. Script-visible state and API objects are frozen; do not attempt to modify them. Values crossing the bridge are JSON-compatible representations of the shared engine types. A callback exception or instruction-budget failure disables that behavior, while other scripts continue. Generated type declarations are at `.rustic/generated/programming/rustic_api.d.ts`; generated files may be regenerated, so never put game logic there.