Twin Spin III
These one-button games offer addictive and accessible gameplay without a lot of overhead. There is no way to save a game or begin at any level other than the first, and there are no sound effects or soundtrack. And still there is a lot of fun crammed under the tiny hood. Click.
If you have never played any of the Twin Spin games before, be sure to check out the first and second games of this excellent casual game series, as well as a more detailed review of the original Twin Spin.