Improvements such as spaceports and arcologies have no trade-off. In general, there is no advantage to not building them. Most don't even consume resources or work units, so there is no reason to not build them as soon as possible.
And if the player doesn't have an interesting choice to make, then it's not a fun game mechanic. We should either get rid of it (improvements are built automatically) or add enough trade-offs to make the choice interesting.
Below are some proposals for making the choice interesting.
Some advanced improvements should consume resources. For example, arcologies should consume trillum and possibly chronimium. Shortages of those resources might cause the arcology to degrade, causing accidents and disasters.
We might also require these resources (in larger quantities) during construction.
Perhaps worlds can have limits on the number of improvements that can be built. Once the limit is hit, the player must destroy an existing improvement to build a new one. Of course, you would still be able to upgrade improvements (e.g., upgrade from a Subtropolis to an Underground Arcology).
This mechanic only works if there are alternatives. For example, using a Foundation world is an alternative to building a Fusion Program. But improvements like a Spaceport have no alternative (unless you don't want to trade).
New Improvement Types
Adding more types of improvements would introduce more choice for the player. Here are some examples:
- Civil Defense Program: This improvement makes it harder for an attacker to conquer the world. Perhaps it adds bonuses to infantry (when defending) or perhaps it introduces new units (units that cannot leave the planet).
- Early Warning Network: This improvement increases the scanning range for the world.
- Recycling Program: Creates raw materials (e.g., hexacarbide) in proportion to durable goods and luxuries consumption.
- Solar Constellation: Creates trillum from solar energy.
This is the current list of improvements:
Spaceport Air Processor -> Domed City -> Sealed Arcology Flare Shelter -> Shielded Habitat -> Shielded City -> Shielded Arcology Floating City -> Ocean Arcology -> Planetary Arcology Hypermetropolis -> Urban Arcology -> Planetary Arcology Life Support System -> Pressurized Habitat -> Domed City -> Sealed Arcology Radiation Clinic -> Shielded Habitat -> Shielded City -> Shielded Arcology Subtropolis -> Underground Arcology -> Planetary Arcology Fusion Program Biotech Program Antimatter Megaprogram (capitals only) Quantum Megaprogram (capitals only) Post-Industrial Megaprogram (capitals only) Armored Constellation Autocannon Constellation Battlestation Program GDM Complex HEL Cannon Network Hypersonic Missile Complex Plasma Tower Network