Super Mario 64 is the game that worked out how 3D platformers should feel. Nintendo released it in 1996 as the Nintendo 64's launch title, and almost everything that followed — the analogue movement, the camera you control separately, the momentum of a run and a long jump — starts here.
You explore Princess Peach's castle, dive into paintings that lead to 15 worlds, and collect 120 Power Stars from challenges inside them. It's non-linear in a way that was startling at the time: most stars can be collected in almost any order.
120 in total across 15 main worlds plus secret stars hidden in the castle. You only need 70 to reach the final Bowser fight, so the other 50 are optional.
It established how 3D platformers work — analogue movement with real momentum, a player-controlled camera, and open worlds with multiple objectives rather than a single route to an exit. Nearly every 3D platformer since borrows from it.
This is a web port of the 1996 game running in the browser. Nintendo sells its own official releases; this page exists because the port runs with nothing to install.