I agree. It doesn't make sense to have Purity 10 and Harmony 10. Yet it is possible in the game.
According to the Civilopedia, Harmoney is about understanding and integrating into the planet's ecology, Purity is about rejecting change and adaptation, while Supremacy is about transcending to a new form of existence that combines technology and life.
But in the game they're all the same.
Gameplay actions should have consequences that shift the player's affinity towards one of the three corners of this triangle. Attacking aliens should take points off Harmony. Researching Habitation at the start should present a choice that establish how your units are initially going to survive on this planet.
- Vaccine - Damage from miasma is reduced by x% where x% is the percentage of movement points remaining when the turn ends. Harmony+1 for choosing this.
- Filter Implant - Miasma is filtered through a nose implant. Damage from miasma is 20% for each consecutive turn you have been standing in miasma. On the 6th turn you take 100% damage from miasma. Supremacy+1 for choosing this.
- Full Body Suit - Completely block out miasma with a full body air-tight suit. Your units are immune to miasma, but aliens will attack your units and trade convoys on sight. Purity+1 for choosing this.
Instead of having the same generators for all three affinities, Harmony should start getting energy from miasma with a building that produces energy depending on the amount of miasma around. Purity should be pulling out their good old generators they brought from earth as tile improvements. Supremacy uses advanced technology to harvest energy from natural resources like Geothermal and Firaxite and Floatstones.
Culture should be obtainable in 3 different ways, too.
Building and keeping Alien Preserves should raise culture and Harmony. Culture for Harmony play should be earned through interaction with aliens and making direct use of local resources (build quarry/plantation/farms). For Purity, it's all about spreading and preserving the human culture, about processing and refining the local resources into materials we are familiar with. So water refineries (building) and habitation domes (improvement) should give culture. All resources will need the Processing Plant improvement which gives points for Purity. For Supremacy, culture is yet to be created. So Supremacy players gain culture through science and production.
Then military units should all be different by mid game.
Harmony should be about swarms. Cheap units that can be merged to form a swarm (to obey the 1UPT rule) to eventually form a very strong swarm. Depending on the constituents of the swarm, it could be stronger against ranged attack or stronger against melee. Swarms should also be extremely terrain dependent, as much as tripling its combat strength on the right terrain. Units occupying basic resources will heal.
Purity should be about logistics. Each unit will have a trailing path to the nearest city/depo for supplies. Colonists can "build depo" when it is within N tiles of a city or another depo. When a unit operates outside supply range, it will gradually drop in effectiveness until at 20% effectiveness it automatically moves away from enemy units towards the nearest depo. Surrounded units cannot retreat. Paratroopers will maintain full effectiveness for 10 turns after paradrop.
Supremacy is about individual enhancement, meaning each unit takes much longer to produce, but will be immune from miasma, need no supply, but heals at much slower rate outside of cities (even when inside own border), etc.
But I guess if we go that far, it's like building 3 CivBE games at once. :3