I had a lot of fun playing this! The idea is creative, and I tried to level 6. I especially enjoyed experimenting with the angles and trying different setups.
One thing I noticed as a player is that when I fail, all the bars reset. I sometimes wished there were faint shadows showing their previous positions, just so I could remember what I tried and make small adjustments ;)
I also naturally tried clicking the gun to fire the bullet after placing the bars, instead of using the start button in the top-left corner. It might feel nice if the gun could also be clicked to start.
Really cool game!