I really like your super cute take on the theme. I died instantly a few times, but after reading the comments I tried some more and found some less deadly enemies and was able to progress and have a lot of fun building my giant lego death machine.
Some ideas that I have, since I see you want to expand this game, are making the time to kill longer (so that you aren't destroyed instantly, and can more strategically target specific sections of enemies or decide to run away) and zooming out the camera when not in build mode, because a lot of my engagements happened at the very edges of my screen.
Great job with the jam, and I'm happy you're expanding it! :D