It's amazing that you did all this in 48 hours. It's really amazing.
What I've been missing were the possibility to know which item does what, when i mouse over a location to place it, I would've loved some position hint (low opacity visual indicator of placement), the hotkeys to these items and the possiblity to remove accidentally placed objects.
On the flip side, I had a lot of fun playing your game and spent more time on it than I want to admit. Great job!