Quantris

Falling blocks that obey quantum mechanics
A Hadamard block puts the piece it touches into superposition: it might be there and it might not. Pieces that share a gate become entangled, so their fates are tied. Nothing is settled until you drop an observation block. Then every entangled piece collapses at once, and you find out which blocks were real.
A line clears only when every block in it has been measured and they all came out the same way: all there, or all gone. Plan for the collapse, or get buried by it.
The quantum state is simulated with the same math a quantum computer runs, so outcomes follow real quantum probabilities, not a coin flip dressed up. You don't need any physics to play. Each mode teaches its rules as you go.
Modes
Marathon: the classic climb, with quantum blocks in the queue.

Sprint: hit a run of point targets as fast as you can.

Ultra: three minutes, as many points as you can get.

Flux: earn energy as you score and spend it on quantum blocks, while you keep the board stable.

Puzzle Vault: hand-made puzzles that need quantum thinking.

VS AI: race a bot at three difficulties.

Two players, one couch
Play co-op or head-to-head on one machine, with two controllers or a shared keyboard. In co-op, two towers share one team score and entanglement reaches across both boards. In head-to-head, entangle your pieces with your rival's, and your measurement can knock blocks out of their tower.
Online
The same co-op and head-to-head modes, against a friend by room code or anyone from the public room list.
Also
Full controller support, with remappable buttons and keys.

Tunable handling: DAS, ARR, DCD, soft drop speed and lock delay.

99 in-game achievements, 40 of them secret.

Replays of every run, and leaderboards for each mode.

Discord Rich Presence.