Pretty good demo so far. The placement for the switches and walls is a little too hardcore for a first level, but I understand that it's just a demo engine.
And I like the destructible terrain too, I just wish there were a way to get rid of the tiny floating bits automatically, without having to jump and shoot a hundred times trying to hit them.
As for the crashes you encounter while using Construct... you really should report those. See if you notice a pattern when it crashes. Does it usually crash while doing the same activity? Are you able to recreate the crash? If so, then post a bug report. The quicker it's fixed, the faster v1.0 will come .
Heck, you could even try crashing it on purpose just to track down the bug.
i wish i could remove then automacally too :/ but i dont think a way to do this :X, if someone can help about this.. xD
and the crashes i think that are already in the bug tracker:
* when i try to resize something, it crashes
* the mirror doesnt work anymore
* opening an object while in event editor results in crash
all of those i think that are on the tracker
and about the Hardness, i dont think thats hard, with the double jump you can easily hit the first switch, or is just me that thinks that? D: