Excellent design but I feel like I'm playing a different game to everyone else, I simply never have enough resources to make it to the midgame. Is that a deliberate restriction on the browser version?
Nope, it's all about careful (or sometimes carefully risky) play. You should try to save breaking blocks for the endgame, for example. Also heart scrolls always give you full health, so they're worth more when you have more heart containers. Learn the patterns of the monsters; try to learn how to guess where the rat king or slime king will be. Things like that.