Nerve

1. 1Thirty items. Twelve of them belong to the day's category.
2. 2Tap one at a time. Every correct tap grows the pot.
3. 3One wrong tap and you lose the lot.
4. 4Stop and bank whenever you like. That's the whole game.

Everything is on screen: the category, how many belong, and the exact odds on every tap. The only thing you're missing is nerve.