Nice game! It was a unique take on a reverse tower defense and it worked really well! Having to manage both a player and some towers helped add to the strategy of it all and it also gave you something to do at the start instead of just watching a couple of towers, so that was a nice addition. Having to have the lines cross the track was kind of confusing at first, but it made sense after a while - and it was actually really fun once a network of them started building up across the map, and you could just sit and watch the chaos unfold. Of course, some more variety - new towers, upgrades, more enemies etc. would've been nice, but the game, as is, is still very fun.
The graphics were nice too and the particle effects helped show what was happening, because it wouldn't have been too clear otherwise what the towers actually did. Music was good as well, and the sound effects were decent too. All in all, it was an interesting tower defense game, and it works great, so well done!