Crack Attack is roughly based on the Super Nintendo game "Tetris Attack". Slowly, your stack of colored blocks grows from the bottom, and you've got to make sure it never reaches the top. If it does, you lose. To eliminate blocks from the stack, line up at least three of one color, horizontally or vertically. Once you do, those blocks disappear, and put off slightly your inevitable demise.
Crack Attack essentially requires hardware acceleration. For XFree users, this means you want DRI.
Disclaimer
It is important to realize that the name of Crack Attack! X-treme play mode is meant to be humorous, and thus should not itself be the subject of derision. Thank you.