Thanks for the feedback!
I don't understand much about slowdown. Does it seem to slow down while preparing to jump, or is the jump speed not fast enough?
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As in it broke up the momentum of the gameplay because I would have to stop & wait for my jump to charge to progress. A double jump would allow for more fluid movement through the level.
BUT: I also observed that it helped enforce the objective, because it would eat up your time and add urgency to you hunting for life-giving flies. So all-in-all, it's probably a good addition.