Once the basic logic gates are designed, it's easy (though tedious and time-consuming) to build arbitrarily large computing devices. One famous example is a multifunction calculator, documented at < http://df.magmawiki.com/index.php/User:BaronW >.
This is the kind of game I would recommend to hackers - it definitely supports the mind set of figuring out the rules in a system, then exploiting them to build something incredible.
For example, I remember discovering that if you build your dwarf fortress in certain freezing climates, it was possible to take water from a flowing source underground, then release it aboveground, whereupon it would flash-freeze into solid walls that dwarves could stand on, tunnel through, or build on top of. That immediately led to Operation: Build An Enormous Ice Palace, a plan to create an aboveground megaplex by making dwarves haul unfrozen water bucket by bucket and pour it, like concrete, into a planned mold. (I was exploiting the loophole that water carried in a bucket does not freeze until dropped from the bucket.)
It was ridiculous, arbitrary, and destructive of my free time - but most games are anyway... so why not take a game that also challenges your hacking mindset?