This was addictive. I played until progress stopped about 1/3 of the way through wave 51. It kept spawning enemies, but no gold or XP were gained. I was at level 179, with just under 13,000 gold.
It could use a bit more of a tutorial or info on the game page about what everything does. I was unsure what the skull and surrounding icons did, and was too busy exploring the main tree to click on them until I was well in and did not want to click on a skull to see what it did. I waited until things stopped progressing to try them, and them had enough to get anything on that tree.
There were some points where I was unsure how much longer I could last, but then I found the LifeSteal skills and focused on them, along with more defense and high health, and from then on it was pretty easy and I started using the higher game speed. The game speed buttons could use with some indication of which is selected, and the same hover effect used on other buttons.
When hovering on an upgrade in the tree, the preview numbers of what it does that shows on the stats looks to be showing about 1 row below where it should be.