Rise of the Triangles is a 24-level vanilla megawad by Ilya (joe-ilya) Lazarev. Project's minimalist theme is attributed to 100 linedefs per map restriction, and its ReadMe story states:

“Low budget alert! It has gotten so bad the environment, and even your head have turned into the least cost-effective shapes to draw; triangles, with each map only using 100 linedefs. You must find the bottle reusing center as soon as possible, and deposit all your used health bonuses, before your world runs out of money and ceases to exist. Unluckily for you the Icon of Sin's (Twin? No. Triplet? No. Quadruplet? No.) infinite-let sister has invaded earth, and swallowed the entire reuse center before returning to hell. You must go after her.”