party-player/README.md

Party Player

A YouTube playlist player for parties. Two browser windows run side by side:

• Player (http://localhost:3000/) — fullscreen poster background with a small video frame that moves around, switching animation on every track (see Animations). Consecutive videos overlap in a 5 second audio/video crossfade, so there is never silence between tracks.
• Queue (http://localhost:3000/queue) — add videos by URL, drag to reorder, delete, see how much playtime is left, and pick the background and animation.

Run

npm install
npm start

Put the player on the projector/TV screen (F11 for fullscreen) and open the queue on a laptop or phone. On the same network, other devices reach both pages at http://<this-machine-ip>:3000.

The player page opens behind a "Start" button. Browsers block unmuted autoplay, so the first click is what unlocks audio. One click per session.

Notes

• No YouTube API key is needed. Titles come from YouTube's public oEmbed endpoint; durations are measured by a hidden muted player on the player page, which is why a freshly added video shows –:–– for a moment (and keeps showing it while the player page is closed). Totals are prefixed with ≥ whenever a length is still unknown.
• The queue is saved to queue.json on every change and restored at startup.
• Settings live in config.js: overlap length, frame size, drift speed, corner screenshot interval and margin, the drag animation's size range, port, and the selectable backgrounds and animations. Anything the browser needs must also be mirrored in the /config.js route in server/index.js.

Animations

The video frame's movement changes with every track. Six animations ship today:

• bounce — diagonal drift, reflecting off the screen edges.
• corners — the frame parks in a random corner and every 5 seconds a screenshot of it appears in the next of the three other corners, going clockwise. The frame never moves, so a screenshot can never cover it.
• drag — a drawn mouse pointer travels to the frame, grabs it near its top edge and drags it across the screen, lets go for a beat, then takes hold of one corner and pulls the frame to a new size. The aspect ratio stays locked and the frame stays on screen, so the resize reads as a window resize rather than a stretch.
• pong — the 1972 game with the frame cast as the paddle: it slides along the bottom of the screen and nowhere else, a square ball runs the diagonals off the walls, and where the ball lands on the frame's face sets the angle it leaves at. The frame is solid on all four sides, so a ball that comes at its flank or up under it is turned away too. It plays the ball's predicted landing spot, but aims a width wide once in a while, and every ball that gets past it puts one on the seven-segment counter in the top right.
• trail — the frame glides along a curving path, steering from waypoint to waypoint, and drops a screenshot of itself every frame-width or so. The stills stay where they were taken and fade over a few seconds, leaving a comet tail of frozen video behind the live one.
• wash — the frame parks in the middle and the colour changes instead: a gradient creeps round the colour wheel behind the poster, taking a minute and a half per lap, and the frame's glow travels with it. The one still animation, which is what makes it worth having between the moving ones.

The queue page's Animation buttons pin the player to one of them, which is how you look at a single animation without waiting for the cycle to reach it. Auto (the default) hands selection back to the shuffle bag. Switching takes effect immediately; while pinned, track changes leave the animation running.

The corners and trail animations ask to share your screen. The decks are cross-origin YouTube iframes, so nothing on the page can read their pixels — capturing the tab and cropping out the frame is the only way to photograph what is playing. The prompt appears once, on the first click of Start; choose this tab. Declining is fine: the frame still parks in its corner and still glides, just without the screenshots. The prompt is skipped entirely on a plain-HTTP origin (i.e. when you open the player from another machine over the network), for the same reason.

Adding animations

#frameMover carries only the motion transform (see public/player/motion.js). #frameSkin inside it is the cosmetic layer, and the two video decks sit inside that. New effects should nest a fresh wrapper rather than sharing a transform with the bounce loop.

An animation is start(context) => stop(), where context is { element, capture } — capture may be null, and is read late, so an animation must cope with it being absent. stop() has to undo everything: timers, listeners, and any DOM it added, because the next animation takes over the same element immediately. Register it under a new name in the ANIMATIONS map in motion.js and in the one in config.js (which supplies the label for the queue page's button), and it joins the rotation.

Selection uses a shuffle bag (createPicker): every animation comes up exactly once per pass, so they stay evenly used, and the same one never runs twice in a row — including across the seam between two passes.