This is the oldest end of the browser shooter scene, and the most reliable. Doom, The Ultimate Doom, Duke Nukem 3D and Wolfenstein 3D run from genuine DOS executables inside a browser DOS environment, so the original behaviour is preserved rather than approximated. Alongside them sit the N64 and SNES clean-room builds, GoldenEye 007, Perfect Dark, Doom 64, Star Fox 64 and Duke Nukem: Zero Hour, which reconstruct the original console code instead of emulating a cartridge. Freedoom and OpenTyrian are the two entries here with entirely free assets, so nothing has to be supplied by you. None of these need an account, and all of them work as single-player.