Gem TD/Gemcraft

If Sid Meier's Alpha Centauri is the heroin of gameplay, the SMAC(k) if you will, then tower defense is the crystal meth. How appropriate then that some of the best games in the genre involve crystalline gems whose interrelated properties weave together in pyramidal symmetry just like the molecular structure of a jewel.

Gem TD has been out for a while; Gemcraft is just released. They both gripped me with euphoric insomnia, coupled with vitamin C depletion, grinding of teeth, and paranoid hallucinations of creeps, endlessly marching. Like all tower defense games, they evoke a superb linearity of thought, a simplified psychology of marching enemies, marching resources, marching upgrades, ever forward, ever higher. I can't belabor this meth analogy enough.

What's interesting is that, while the two games seem very similar, in terms of their actual formal structure, they're almost orthogonal. Gem TD involves an optimization of a closed area, the way you carve the spatial path and the high-level combinations of already high-level gems defines the winnable strategy. Gem TD is the numerical equivalent of building a tower; every move not only affects your continual survival, but builds the foundation for your long-term victory. Gemcraft, on the other hand, is practically horizontal. The combinations of gems carry a trade-off between conservation of space and efficacy of each color's particular effects, but because this stacking mechanic is local to a single instance of a single battle, it doesn't make as much difference in the long run compared to the experience points you gain. Like the game's scrolling map, Gemcraft is mathematically horizontal, and to that extent, much more casual (it even comes with a save feature).

So you could say Gem TD is like injecting meth, and Gemcraft is like even mixing it with water. I recommend you do both this weekend.