

Īside from coming from a different religious angle, one of the major points of the game was to pay homage to Space Invaders, one of the first commercially successful shoot 'em up games. There are numerous references to Bishamonten throughout, as can be seen from Shou Toramaru and Nazrin's background stories and Ichirin Kumoi's clothing design. Unlike previous games, which have focused mainly on giving the player a Shinto feeling, ZUN designed this one with Buddhism in mind from the very start. Scoring generally involves timing UFO outbreaks well and utilizing point-based UFOs over the others.

Certain enemies will release a UFO upon destruction, which the player can collect to obtain more bombs, life pieces, or point bonuses. Undefined Fantastic Object's main gimmick lies in the colored UFOs. Unlike Mountain of Faith and Subterranean Animism, the bomb system from earlier games such as Perfect Cherry Blossom and Imperishable Night has been reintroduced. Undefined Fantastic Object features three playable characters ( Reimu, Marisa and Sanae), each with two weapon types. Main articles: Gameplay, Strategy, and Spell Cards
