This is RE-DOOM, a cloned version of DOOM remade in Gamemaker.
When in-game, type these cheats in:
CHEAT EFFECT
urgod - God Mode
urnoclip - No Clipping Mode
gunnernutter - All weapons and full ammo
gatekeeper - All keys
healthfreak - Full health and armour
ilikebigguns - Secret Weapon
theolddays - Ragtime DOOM Mode
discodoom - Disco Mode
icantsee - Fog of Death Mode
killall - Kill all enemies
itsalive - All dead enemies live
uksdebug - Brings up the debug menu
urdead - Kills the player
interpolateme - Interpolates the textures
nothappywiththat - Peter Mode