Bastard Child of Minesweeper and Sudoku
Shellblast is kind of like a cross between Sudoku (where columns have to tally) and Minesweeper. Each bomb is a puzzle with randomly placed "pistons" which must be properly identified in order to diffuse the thing. Though the game is played on a grid, each puzzle uses a different "shape" for its bomb. Though there's no real difference between a tile which isn't used in the puzzle and one which is used in the puzzle...