Compete against other players for the fastest completions on several challenges and story modes.
Slow to understand at first, you get to learn the hidden mechanics through experimentation. It is a fast-paced game and a bad move won't cost you too much time. Each mode is designed to be completed again with a better and more efficient strategy.
Also if you want to play casually, upgrades are bought for you, not in an optimal fashion but enough to allow completions without much thinking.
Expect a weekly update that should include crash fixes, new challenges, more clear user interface, and new story modes.