Platformers translate unusually well to the browser because they need a keyboard and almost nothing else. PrinceJS reimplements the original Prince of Persia in HTML5, sm64js is a JavaScript port built from the Super Mario 64 decompilation, and Sonic the Hedgehog 2 and Banjo-Kazooie arrive as clean-room builds. Most of these run at full speed on a laptop that would struggle to emulate the same hardware.