The game is good, but, the enemies have way too much HP, and with a basic combat system it's just spamming space.
Expanding on the combat should make the game way more fun, but fixing the enemy HP is really important.
Espacially when the boss deals two bars worth of damage when the player deals like 1/20.
That being said, I understand that you put a large HP because you recruit other soldiers to fight with you. So another fix is adding more soldiers, but that is the same as lowering his HP.