Just to let you know, I turned this into a full game since I made this prototype six years ago and I'm releasing it this month on Steam! You can check it out at http://store.steampowered.com/app/499140/Operator_Overload/ - Glad to see people are still enjoying the original prototype ^__^
The reason a block falls sometimes is to stop a player from moving a block too quickly, as they are then able to move the block through a collision and out of the map. Unfortunately it's one of those things that I had to hack fix quickly in the small time I had :(
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