A really great Puzzle Bobble game.
If you don't know what a Puzzle Bobble game is:
At the top of the rectangular playing arena, a number of bubbles of various colours are placed in a prearranged pattern at the start of the level. At the bottom of the screen, the player controls the angle of a fixed cannon that fires semi-randomly coloured bubbles in a straight line. The bubbles, when fired, travel in straight lines, possibly bouncing off the side walls of the arena, before eventually coming to rest either touching one or more of the existing bubbles, or at the top of the arena.
If the bubble manages to come into contact with identically coloured bubbles, forming a group of three or more, those bubbles, and any bubbles hanging only from them, are removed from the field of play, and points are awarded depending on how many bubbles are removed from the screen at once.
An exponential scoring system is used, leading to large rewards for removing many bubbles at once.
As the game proceeds, the top of the playing arena, and all the bubbles, move down the screen after a certain number of bubbles has been fired. The player must remove every bubbles from the arena before any pass a line at the bottom of the arena.