Building Optimization (EU2012)
Your base is a 7x4 grid of spaces for construction. The center row is reserved only for the ACCESS LIFT, which leaves 24 spaces you can build on(though three start prebuilt). You cannot build at a level that does not have an access lift. While some squares may start empty, most will be filled in with rock, which must be excavated (taking 5 days) before any construction can begin.
Digging deeper costs more, but Steam Vents are usually situated further down; also, more dimensions allow you to take more advantage of Adjacency Bonuses earlier in the game. A good example is to build down to a steam vent early, build a Thermal Power Generator, and then build normal Power Generators adjacent to it to maximize the efficiency.
Adjacency bonuses are awarded once for each pair of facilities that are adjacent to each, which means that square formation is the optimal formation for facilities that have adjacency bonuses, since this is hte only formation that will give you four adjacency bonuses for four facilities. Since you have to build an access lift in the middle, you are left with space for two squares of facilities and 4 individual facilities on each side of the lift. No matter how tempting it may seem to build an optimal base like this, arranging satellite support, workshops, labs and power units in squares, the cost of such undertaking will be a huge deterring factor. Since you absolutely need workshop, power source and satellite facilities from the very game start, you would have to excavate to level 3 right at the beginning, which would cost you extra 4 power and $ 140 (effectively, $ 180), plus extra maintenance for the extra access lifts. Therefore, it makes sense to have one of the three to be built in another formation.
To get complete satellite coverage, the most economical setup is two Satellite Relays and two Satellite Nexus arranged in a square. However, if you build 3 SR and 1 SN in a square, you get support for 14 satellites. Since you need to support 16 satellites total, and on higher difficulties you are most likely going to lose countries, this seems to be a viable alternative.