Littleroller; Phantom Capsule

A Rules-light Print'n'play tabletop strategy game for 1 or more players, Phantom Capsule revolves around piloting middle-sized robots in defense of a city plagued by monsters.
The game pieces are all constructable papercrafts.
All game-pieces and rules are free and available for download.

Gameplay centers around logistics, in that players decide what to focus their robot's precious energy on before the actual action phase begins.
The monsters operate on rudimentary AI, and largely govern themselves.

The goal of each mission is variable, but typically the player/players must work together to defend a single power plant from invaders. There are also rules for direct competition between players, which gets messy very quickly.