SpaceChem is very likely the ultimate in puzzle games. You use command instructions to guide waldos in constructing chemicals. That's the short version. The long version would take a very long essay to describe.
If you like puzzle games - especially puzzle games cloaked in the trappings of simplified science & programming - give the demo a shot. It's well worth it.
Word of warning, though, if you do get into this game you will have entire days of your life disappear into it. I also have to be careful not to play it in the evenings or else I end up dreaming all night about how to solve SpaceChem problems.
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Edited By TPRJones on 1296845880