Clickomania! is not aptly described as a SameGame clone. It is more like a combo of the various SameGame variants in existence.
By default, the goal of the game is just to remove as many blocks as possible from the playing field, preferrably all of them, like Roof Rats without the tenants. This is called low score mode. If you enable high score mode, it is the number of blocks removed in one turn that are most decisive for your score, just like the original SameGame.
If you enable auto drop/count down, Clickomania! becomes more like BreakThru!, with a time limit and single stones moving along the top row that you can drop down, and that sometimes fall down by themselves. For even more BreakThru! features, enable special stones and you'll get the equivalent of coke cans and bombs.
Clickomania! is highly configurable. You can set the rows and columns between 8 and 40, independent of each other, the size of the stones is 550px, again height and width seperate, and you can choose between 2 and 15 colors. Stones can have solid colors, be textured or translucent (this is called voyeur mode), and you can choose if lines surround every block or groups of blocks of the same color.