The game's too hard in the beggining - the game is super punishing; doing 1 mistake and having to do everything over again is super feel-bad for the player; the base should have more than 1 HP.
That aside, I like the idea of "less towers = more score"; it means the player is incentivized to fine tune their defense rather than just spam the most cost/efficient tower. It gives a different dynamic to the genre that I greatly appreciate.