Timers, sounds, menus and animations as components

Timer, AudioSource, UI nodes and AnimationPlayer: whole jobs from plain data.

Four components do a whole job from plain data, with no system of yours (scene files and the editor's node kinds are made of them). Each sends an event whose entity is the node it happened to.

• Timer (core): Timer({ waitTime: 2, autostart: true }) sends TimerTimeout every 2 seconds (once with oneShot). Use it for waves, cooldowns and spawns rather than counting time.dt yourself.
• AudioSource (Audio()): a sound that belongs to an entity. AudioSource({ sound: 'assets/fire.ogg', loop: true, autoplay: true, positional: '2d', range: 12 }) pans and fades with the camera ('3d': around it). playing is the switch; AudioFinished when a sound that doesn't loop ends. A one-off effect is still audio.play(name, { at }).
• UI nodes (UI()): a menu or HUD as entities, a Control (Control.preset('bottom', { w, h, margin })) plus UiPanel, UiLabel, UiButton, UiSlider, UiToggle, UiTextInput and UiBox rows and columns. They are themed, scaled and kept clear of the platform's corners like views; a click on one never reaches the game; keys and a gamepad move focus; modal: true makes a menu. Read UiPressed, UiToggled, UiChanged, UiSubmitted. A view (ui.view) is still the quickest HUD in code.
• AnimationPlayer (Animation()): keyframes on the nodes around it, from anims/*.anim.json (parseAnim checks one): fields eased between keys, call and signal keys, loops and crossfades; AnimationFinished when one ends. Name the nodes it moves (world.spawn(list, { name: 'Door' })): tracks find them by path from the player's parent.
• Files a scene uses with no code: a sprite sheet is a *.sheet.json ({ "image": "assets/hero.png", "frameWidth": 32, "frameHeight": 32, "clips": { "run": [2, 3, 4, 5] } }) that a Sprite names as its image (a SpriteAnim plays its clips); a TileMap paints tiles (rows of tile numbers, "0 1 . 2", from its start cell) from a *.tileset.json ({ "image", "tileWidth", "tileHeight" }); project.json's audio.effects names synthesized effects an AudioSource plays like 'coin'.
• In a test, game.run(seconds) plays them all, and ui.nodes.press(button), ui.nodes.type(input, text) and ui.nodes.setValue(slider, 5) do what a player would, with or without a screen.