Open the Spotify Developer Dashboard and create an app (needs the app owner to have Spotify Premium). Tick Web API and Web Playback SDK.
Add this exact Redirect URI to the app:
Paste the app's Client ID below. Add everyone who will log in under User management (max 5 in development mode).
The person who logs in needs Premium too, because the browser plays the full song through Spotify. No server is involved; your login stays in this browser.
Just want to look around? (silent, 8 built-in songs).
Press SPIN (or the space bar) to pick a challenge.