Bucket is a line-clearing puzzle game based on Welltris by Alexey Pajitnov.
Like other games of its kind, tetromino pieces fall from above, squares are cleared in complete lines, and the game gets harder over time by getting faster. However, there's one big twist.
Instead of a tall board with pieces falling from the top, the game board is a square in the middle with a rim surrounding it. Pieces can fall into the board from all four sides, and lines can be cleared vertically and horizontally.
(See RULES.md for more info.)