Blocster

Blocster is a singleplayer puzzle game. The game is played on a 20×16 grid of
pieces. The idea is to swap adjacent pieces to create groups of identical
pieces that align with open space. These pieces then disappear until the board
is fully cleared. The player must not leave blocks of unswappable pieces
behind, as this renders the level unfinishable, requiring a restart. Single
pieces left isolated turn into jewels and attract a bonus score. The game is
played for fastest time, highest score, or most jewels collected. Scores can
be logged to an internet leaderboard.