Thanks for your feedback!
As for the hit indicator, I think the trouble is there is no tutorial yet for explaining that weapons can be "swung" as in, click then move the mouse around, everything that the weapon swings into will be hit, you can visualize this by pressing F9.
I'll add the ability to close the recipe book with ESC. Thanks for mentioning it.
There are more powerful orbs, just not in the demo, the +2 and +3 versions drop from harder mobs. I also have considered doing a combination recipe to upgrade them.
Getting the balance right is hard. I've actually lowered the difficulty considerably since many people have trouble at first and I have played way to much so my gauge of difficulty is off. Enemies spawn based on highest player level, so adding a different enemy with higher stats later in the game to keep it fresh is doable.
Right now the Blobby boss shoots more and more blobs at the player and the number of them is not capped. This is probably what was causing the lag. I'll consider capping the spawns or despawning the remaining slimes when the player defeats the boss.
Stay tuned for more updates.