Make a game about religion. Christianity, Islam, some ancient shamanistic belief, or your own fantasy religion, anything related to spirituality and organized faith. 

Make your player a priest, a heretic, a crusader, a scientist making robot angels, or a poor little girl. Fight the pope, kill Buddha, burn infidels, enforce Sharia law. Whatever it is, make it interesting.

Any engine is good but when in doubt just use RPG Maker. You have a month. Scope accordingly and don't cram until the last minute. Please post progress.

Rules

As always, one hard rule: have fun. Good luck!