I found the shadow, it's like, right there guys
GemCraft is, mechanically, an excellently well-crafted tower defense game. And basically nothing else.
There is a plot in GemCraft, allegedly, but even if it wasn't face-palmingly generic - wizard gets screwed over by dark magic; film at 11 - the game simply doesn't make a case for its relevancy. A cartoony tower-defense game like Kingdom Rush may not feel smart, but the way it intertwines its theme with the level-to-level gameplay lends it an air of charming continuity, at least.
GemCraft has technical polish to spare, with a bevy of mechanics to explore (although none seem as effective as straightforward gem upgrades), but no charm at all to speak of. Everything in the game is intentionally flat and uninspiring, so it can get out of the way of raw, calculated tactics.
To die-hard tower defense fans, GemCraft offers expert-level mechanical design and plenty of content to master. To everyone else, though, there's practically nothing to love here. A few minutes of entertainment, at least -- but nothing that makes you wonder what might happen in the next level.
Progress: Wizard level 36, 21 fields explored