I've finished the whole thing, nice music btw (it has a vibe to it), there are multiple ways to finish a level (intentional or not) that makes the level design really good. If polished this can make a fully fledged game, there are some thing to clean up first though: camera is too slow - make is so when I hold shift for an example that the camera goes faster, don't delete all my placed objects when I fail, and lastly proper art for menus and the game itself - consider make everything the same resolution (place everything on a single canvas and make it's size compared to the player sprite) 16x16 or 32x32 resolution should do nicely (you can watch some videos from "Pixel Overload" on Youtube he makes pixel art related videos).
P.S. If you're reloading a scene when you fail - save objects positions then place them again. They are a couples of ways you can do this - I recommend you to use static list that saves which object is placed where (like a struct with name of the object or object itself and Vector2 for position) so you go trough the list and add objects to the map while taking away the currency for placing them.