The building track part was suppose to be more expanded upon initially, but we didn't get the time to fully implement everything.
Which is where the gameplay loop comes into a problem as well, since initially the lanes/tracks were suppose to be given for free after every wave and you having to clip it together with an existing track.
Having to try out the game myself, it seems like you can only get so far into the game, I'll see if I can convince the programmer , to make it a bit more playable , by either nerfing the track cost or buffing starting money, preferably both .