Fun game, the music sounds like it's taken straight from an 8-bit Mega Man game.
The Drag-and-drop could use some tweaking, in my browser it had a really hard time registering, and I almost completed my first full run not realizing I could even move towers because nothing happened when I clicked on them (turns out the game is a lot harder when you can only go up to level 2 towers, and your first ones get deleted)
Overall very enjoyable though, played through it fully a couple of times once I got the hang of it