This game has some nice progression. different train carts, multiple enemies. But in the end I was quite bored after getting through the 2/3 min mark. I got to 7mins and nothing was really coming that close. It took me a while to realize that the hp upgrades aren't for the train. I though for a long time that the enemies are attacking the train. Still I have no idea how the two hp powerups work. For 4 mins straight the rightmost tower had the same health all the time. Not sure why