If you have five spare minutes, Worm Crawl will fill them. Everything happens on one screen with a starting step of 200 ms that tightens as you eat, and the whole thing runs straight in the browser - no downloads, no sign-ups, no fuss.
Steering is the whole game: swipes on touch, arrow keys or WASD on desktop. The input queue accepts two turns ahead, which means a well-timed double turn can thread a gap that looks impossible at first glance.
Nothing here needs a tutorial or a wiki. Controls are one gesture, the goal is one sentence, and the difficulty comes from execution rather than homework. That is exactly what a browser game should be.