This is an old tower defense game I wrote a while ago to test out cloning. Click on a tower and drag it to where you want it to place it. The number on the tower is the cost. Please note that you can place towers in the track. Also please note that the game never ends. It just keeps going until you lose or get bored.
One final warning is that I wrote this a long time ago (i.e. 2014 or so) and haven't modified it since then, so there are probably a lot of bugs in it. If you put the orange tower in the track, it will crash the game since it's the same color as the end of the track.