For the prototype, though, I’d focus on movement. The decaying platforms should be pretty simple to approximate well enough:
– each unit of platform has N (10?) levels
– each unity of time on it, you deduct health, knocking off levels as you cross steps of damage
– have N (10?) textures for each of the levels of health that you swap in
In a “real” game you’d need to worry about making the borders match (level 2 next to level 5 would match using “these” texture combos) but I’d just ignore it and let the borders be discontinuous

The movement needs to satisfy whatever feel you want: somewhere between twitchy and easy/nimble to control. How does the movement through air work? Do you damage platforms if you hit them from below? If so, do you make it easy to control the arc of your jump to avoid hitting them from below?

I’d also consider an XBox controller: you could then move around while firing acid in any direction … would be satisfying to spray willy nilly while destroying teeth and the level.