I thought I'd be too dumb to play Dominoid (seeing as I prefer fast Tetris to a more long-term-thinking Puyo Pop), but found its mechanics tempered with forgiveness. If you bungle a 'ring' (a loop of alike dominoes around other sorts), you can still save yourself by slapping on a simple 2 x 2 clear.  The small clear with also erase any messy tower of alike dominoes surrounding it, like smoking out an ant colony's tunnels.

This single mechanic makes the game's specific draw (clearing rings) accessible without compromising on challenge.

Within this game's construction are many thoughtful touches to the player, like being able to easily edit music with ogg dumps. The music itself is great, and ranges from eerie-yet-calming dawdles to faster, poppier tracks when you ascend levels and the game picks up speed. You can choose from alternate backgrounds and even-more concrete tile types. I admit I'm much better parsing patterns of colorful moons and clubs than counting dots on a domino.

Paid for my copy after my entire household got it. Most of us aren't puzzle people, but we keep coming back to it in short bursts, and visibly we've gotten better at carrying the weight of higher levels even without a practice mode. 

We realized we didn't need a practice mode or marathon mode. There is only one mode, and that's play. That is the confident distillation and attention-grabbiness of a pick-up-and-play arcade game. It's probably also easier to make it that way.