PSP games running in the browser without an emulator. The game's MIPS machine code is translated ahead of time into C++, compiled to Web Assembly, and linked against a small reimplementation of the PSP's operating system and graphics chip that draws with Web GL2.
The first title brought up this way is God of War: Chains of Olympus. It plays from boot through the menus, cutscenes and combat, at 60 frames per second in the scenes measured so far in Chrome and Firefox on a laptop, at up to four times the PSP's resolution, and on phones with on-screen touch controls.
God of War: Ghost of Sparta followed through the same scripts. It needed the PSP's DRM decryption for one small file, a handful of system calls and a lighting fix, and no performance work: it runs at 55 to 60 frames per second at three times the native resolution. No game data is included here.
The first playable build ran at 6 frames per second. Most of the way to 60 came from finding out where the time actually went rather than from making the renderer faster.
Source: Hacker News · Summarized by HeadlinesBriefing