If you have five spare minutes, Night Flap will fill them. Everything happens on one screen with gaps that start at 36% of the screen and shrink with every point, and the whole thing runs straight in the browser - no downloads, no sign-ups, no fuss.
Scoring is per pipe, and the difficulty comes from variety - gap heights drift up and down the screen, so no two pipes arrive the same way. The ramp is honest: nothing suddenly teleports, the world just stops forgiving lazy taps.
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.