Complete the core
Pieces fall normally. The moment one locks, the whole chamber turns a quarter turn. A row or column only clears when it is complete inside the dashed square in the middle — fill an outer row and nothing happens. The counter under Core lines shows how many you need.
Entry pressure and vents
New pieces enter through the shaded band at the top of the chamber, above the dashed line. Entry pressure measures how full that band is. Spend a vent to wipe it clear — tap a diamond, press V, or use a bumper. If a piece has nowhere to enter and you have no vents left, the run ends.
Which way it turns
The arrow beside Next shows which way the chamber turns after the current piece locks. By default the game picks whichever direction leaves less stacked near the entry. You can force clockwise or strict alternating in settings.
Landing
A piece that lands gets a moment before it locks. Moving or rotating during that moment cancels it, so you can slide a piece under an overhang after it touches down.
Saved locally
Your best score and preferences stay in this browser. Spin Stack makes no network requests and sends no game data anywhere.