140 is a minimalistic puzzle platformer where timing is often tied to the rhythm of the music and visuals. The player controls a white cube that can go left, right or jump in an abstract environment with pulsating visuals and music. The cube changes form based on movement; it turns into a ball going left or right, and into a triangle when jumping. This is purely an aesthetic change and has no influence on the gameplay.
The game consists of three large levels divided into smaller sections with checkpoints. To progress various platform puzzles need to be completed. These include regular jumps, temporary and moving platforms, grey parts that cannot be touched, temporarily reversed gravity, platform movement based on sound and more. To complete a section a small ball needs to be collected. When it is brought back to a large container, the next section is loaded. Each of the three levels ends with a boss encounter, each time with a completely different mechanic to defeat them.
When the game is completed a mirror mode is unlocked where each of the three levels can be replayed in reverse. In addition these need to be completed in one go as dying immediately returns you to the main game hub.