Cube

Cube (2002): Shooter. Developed by Wouter van Oortmerssen. Available on PC (Microsoft Windows).

Cube is a freeware 3D first-person shooter game. It can be played both in multiplayer and singleplayer mode. It allows the player to edit maps in-engine in full 3D, this means it is possible to fly around the map, point and drag to raise/lower blocks, create slopes etc. Multiple online players can even edit a map simultaneously.