Great implementation of classic TD!
Really enjoyed the tower upgrade system and design. They're quite thematic and interesting, especially how they change quite drastically depending on upgrade path. The flavor text is also pretty good.
I would play the s*it out of this if the planned meta upgrades were just as interesting as the tower designs.
My main gripe with this game is the lack of info: how big is the kobold bonus? Which towers are buffed by the kobold ability? How much burn does the first flame effect upgrade give vs skipping to the second one? How much health does the spider web have? etc
Also, it really should be mentioned somewhere that lava turns into walkable but un-buildable tile when the wyrm dies.
Finally, a "bug" with the spider (ba-dum-tsss). The web doesn't become larger after range upgrade until the previous web is destroyed.
Great game, can't wait for updates!