Open source, Open mind.
Mutatris in Java

This game is a combination of elements from tetris and columns. Line up 4 or 5 blocks in a vertical or horizontal line of the same color, or a rectangle of the same color and they disappear. Blocks move down when there is no block beneath it. Swap the colors of the blocks to find the right combination.

Controls

Left, and Right and Down arrow keys to move the blocks.
Up arrow key to shift the colors.

You can also click on a valid location in the grid to move the block there.
View Source Code