If you have five spare minutes, Hexa 4096 will fill them. Everything happens on one screen with a 6×6 board where the target tile is 4096, and the whole thing runs straight in the browser - no downloads, no sign-ups, no fuss.
The strategy sits in corner play: pick one corner, keep your biggest tile parked there, and never swipe it into the middle of traffic. With a 6×6 board where the target tile is 4096, the margin for error changes - more room means longer games, less room means every swipes counts twice.
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.