Really great project. Obviously for this to be a full game you will need multiple maps and maybe upgrades for the towers, but for a Jam game this is a great portfolio piece that you should definitely continue with!
Some general ideas to improve the base game would be:
The ability to click on the towers and be able to remove them.
Improve how you handle playing sound (10 lazers all going at the same time is a but much :P)
Really great job, keep it up!