Sine Mora is a side scrolling shoot ’em up game. The player controls an airplane along two axes while attacking enemies. The gameplay world is rendered in 3D, and at key points an in-game cutscene plays in which the camera and plane move. These are often transitions into another part of the gameplay world, but are also used to give the player a new perspective for things such as boss battles. The plane’s primary weapons can be upgraded, and players are equipped with a limited-use, more powerful secondary weapon to eliminate more on-screen enemies at one time. Consecutive kills with the primary weapon will increase the game’s score multiplier, while use of the secondary weapon or time manipulation will reset the multiplier. The player’s final score is determined by a number of factors including kills, damage taken, and powerups collected.
As the game is marketed as a bullet hell shooter it features four difficulties: normal, challenging, hard and insane. The normal difficulty reduces the on-screen ordnance from enemies, while the insane difficulty is geared towards those who are veterans of the genre. In this difficulty the ordnance on the screen is much higher, forcing a greater difficulty level. In addition, four game modes are included: Story, Arcade, Score Attack, and Boss Training. Story mode is the primary mode of the game and allows the player to see the narrative as the game progresses. On the standard difficulty players are given eight continues, while the Insane difficulty yields only five. Completing levels on the more challenging difficulty unlocks an alternate narrative. Arcade mode removes the narrative cutscenes and limits the player to only three continues. Score Attack mode allows players to replay any stage previously completed with only one life. The objective is to achieve the highest score possible and complete the stage. Players do not progress to the next stage after complet.