Great game! Took me a good 2 hours straight playing it to finish every level! But the hard difficulty is from cheap bottlenecks in levels and enemies that come to you too fast (don't get enough warning/time to react). Only very few will fully understand how to use the player's constantly accelerating movement mechanics properly, so I recommend having the ability to accelerate & decelerate. Lots of content, great boss battle, enjoyed it heaps.