If you have five spare minutes, Mine Bubbles will fill them. Everything happens on one screen with spawn waves every 0.66 s at level one and a 24% bomb cap, and the whole thing runs straight in the browser - no downloads, no sign-ups, no fuss.
The temptation is to pop everything on sight - the scoreboard disagrees. Big multipliers come from patience: let a cluster of same-colour bubbles gather, then pop them in one deliberate sweep while the combo timer is still warm.
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.