I like trains! It reminds me a bit of Choo Choo Defenders, though that's a pure autobattler.
A lot of enemies are reaching the middle and the rail loop is fast enough that it could have been a static TD in the middle. I'd make use of the rails, make them longer and reach more diverse areas, enemies move slower and this way the train cycle brings hope of killing X on Y on the other side of the map.
Also you could try save settings in PlayerPrefs, they reset after each refresh. The game has a bug with fullscreen toggle, it often bugs and hangs when maximized. It didn't work on ultrawide so I had to play it minimized.
GL HF with your game <3