On the first level alone, there’s a huge section that only secret-hunters can see, a massive aerial segment filled with floating containers to clamber over and barges to ride around. I didn’t see it at all until my second playthrough.

As for the controls, they behave a lot better if you just plug in a gamepad. The mouse controls are better than most, but platformers (especially ones as reliant on analogue precision) tend not to do too well with a keyboard for this reason.