Tips and Tricks
Look for uneven patches of ground, particularly in otherwise-featureless environments - that's usually where you'll find hidden areas.
Collect as many blue seeds as you can - you'll need them for the more challenging sections, and they keep checkpoints powered-up.
On your first attempt at a level, take things slowly to avoid unhappy landings. You can always plummet at speed through them on a second run.
During the first boss fight, take care not to fall through the gap when dislodging the rocks in the central bridge. Also, watch out for dust gathering on the ground, as that's where the tentacles will pop up, killing you instantly.