Got stuck in the fire cave. If you don't get the gold key you can still get all the way through to the tree with the hole in it. And then it's impossible to get back. Be warned.
A good start. I'd recommend adding some sound and music, a keyboard shortcut (or click) to delete placed pieces, and the tutorial stuff to not pop up when you reset the level. Also it's pretty short and a bit on the easy side, but that's not necessarily a negative. 2/5 until a solid functionality update occurs.
This game wasn't too hard, which is a rare quality in a game like this. I truly feel that mouse control doesn't belong in bullet hell games, however. Bottom path appears to be easy-mode. That shield is just far too good. Should put the bars and stuff in a black box below the playing area. They get in the way whilst trying to dodge bullets down there. The pods shouldn't block the bullets because this prevents graze, which should be an integral part of the game. If you HAVE to go with mouse control, at least make the game pause or lock when you mouse out of the game area instead of just stick your ship to the side to be blasted at the whim of the enemies. I think that about covers it. Make more bullet hell games, please.
Level Editor, for sure. This is a great start but I think A LOT could be done with placing marbles on the map instead of just "drop this one, then this one, then this one." Need more difficulty! Great game, hope to see more in the future.