Here is the full list of all 12 Rounded Hills achievements.
100 Coins in your pocket.
1000 Coins in your pocket.
Reach a score of 200.
Reach a score of 350.
Reach a score of 1000.
You died while having a score of 0.
Buy the cheapest ball in the store
Buy a ring ball.
Buy the red ball.
Buy the green ball.
Buy the blue ball.
Reach a score of 100 without collecting any coin in a round.