There are a lot of small errors in explanations of the mechanics but this is just a quicklook. Reading the full tutorial will explain most of it but this is a weird and different type of game that takes some time to wrap your head around.
Most of their platforming problems seem to be just lack of any confidence in how far or high they can jump. With the hover they can clear so much distance but they just second guess every 3 foot jump. Abby seemed to get the feel of it at the end of the red coins.
Is that fall through world thing in Sonic a common bug? I saw the same exact thing where sonic is just being pushed right on that path though the wall in several streams and lets plays.
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