DOOM® CAPTCHA

How it works

A CAPTCHA that lets you play DOOM® to prove you’re human (for
educational and entertainment purposes)

The project works by leveraging Emscripten to compile a
minimal port of Doom to WebAssembly and enable
intercommunication between the C-based game runloop (g_game.c) and the
JavaScript-based CAPTCHA UI.

Some extensions were made to the game to introduce relevant events
needed for its usage in the context of a CAPTCHA.

• Started out with a minimal, SDL-based port of Doom that
  can be efficiently compiled to WebAssembly
• Tweaked the build to make it compatible with the shareware version of
  wad (doom1.wad) for legal use
• Introduced new unofficial process flags:
  • -nomenu (m_menu.c)
    to skip the main menu and jump straight into the game
  • -autoreborn (p_mobj.c)
    to automatically rebirth the player after a 2s delay
• Introduced callbacks into JS land to be used by the
  CAPTCHA UI:
  • onPlayerBorn when the player is born or reborn
  • onPlayerKilled when the player is killed
  • onEnemyKilled when the main player kills an enemy
• Tweaked the default process flags in
  d_main.c
  to make the game more challenging:
  • -skill 5 sets the difficulty to “Nightmare!”
  • -fast makes it even harder
  • -warp e1m1 jumpstarts the game to where the action is
  • -nomenu doesn’t let the player trigger the main menu

See the v0 UI generation
or
get the source.

Built on the shareware version of DOOM® released publically for
non-commercial use. DOOM® is a registered trademark of id Software
LLC, a ZeniMax Media company.