6.6 KiB
Terrain System
Tile structure
Each hex tile carries one terrain (plains, forest, hill, …) at the data level — terrain fills the tile uniformly. The perceived boundary between two adjacent terrains is the shared hex edge, which is the edge slot between the two tiles' centres. This is the biome contact membrane: a unit deployed to its own edge keeps its parent tile's terrain bonuses (forest cover on the attack), and combat between two centres resolves at the shared edge.
For the centre + 6 edge slots model itself and how it governs combat, flanking, and ZOC, see ../HEX_GEOMETRY.md.
Terrain Types and Base Yields
| Terrain | Food | Production | Gold | Cultural resistance | Notes |
|---|---|---|---|---|---|
| Grassland | 3 | 1 | 0 | 1 | Best farming, flat |
| Plains | 2 | 2 | 0 | 1 | Balanced, easy to traverse |
| Hills | 1 | 3 | 0 | 2 | Good production, defensible |
| Mountains | 0 | 4 | 1 | 5 | Best production, near-impassable |
| Forest | 2 | 2 | 0 | 2 | Cover, lumber |
| Jungle | 3 | 1 | 0 | 3 | Rich food, hard to traverse |
| Boreal Forest | 1 | 2 | 0 | 2 | Timber, cold |
| Enchanted Forest | 1 | 1 | 2 | 4 | Supernatural resistance |
| Desert | 0 | 1 | 2 | 3 | Harsh, trade routes |
| Tundra | 1 | 1 | 0 | 3 | Marginal land |
| Swamp | 2 | 0 | 0 | 4 | Dangerous, hard to build |
| Volcano | 0 | 5 | 0 | 6 | Extreme production, almost uncrossable |
| Snow | 1 | 0 | 0 | 3 | Harsh |
| Ocean | 0 | 0 | 2 | — | Naval only |
| Coastal Waters | 1 | 1 | 2 | — | Fishing, trade |
| Lake | 2 | 0 | 1 | — | Food, inland |
| Inland Sea | 1 | 1 | 2 | — | Naval, trade |
Cultural Resistance
Culture spreads along the path of least resistance. Expansion weight formula:
Weight = (Culture pressure) / (Resistance × Distance)
The city expands toward wherever pressure-to-resistance ratio is highest. Plains and grassland fill in naturally. Mountains require deliberate investment — either gold (tile purchase) or Pioneer preparation (reduces resistance).
Pioneer preparation reduces resistance, not adds weight. A Pioneer working an unclaimed Mountain tile for 3 turns reduces its resistance from 5 toward 2. The tile becomes reachable rather than more desirable.
Tile HP System
All tiles — surface and underground — have structural integrity that can be degraded by siege bombardment, geological events, or deliberate demolition.
Surface Tile States
| State | Description | Effects |
|---|---|---|
| Normal | Full HP, undamaged | Standard yields and movement |
| Damaged | HP reduced | Buildings take structural damage, -10% yields |
| Cratered | Heavily damaged | Impassable to Cavalry and Siege; infantry -50% movement; -25% yields |
| Sunken | Surface dropped in elevation | Terrain type changes (Mountain → Ravine, Plains → Depression/Bog) |
| Ruins | Fully degraded | All buildings destroyed, uncapturable, uninhabitable |
Terrain Failure Modes
| Terrain | Sunken result |
|---|---|
| Mountain | Ravine (impassable, no building) |
| Hills | Damaged Plains (flat but rough) |
| Plains | Depression / Bog (waterlogged, movement penalty) |
| Forest | Scorched Earth (no cover, no yields until recovery) |
| City tile | Buildings lean/collapse, underground may be exposed |
Cross-Layer Interaction
Surface and underground damage feed each other:
- Heavy surface bombardment weakens underground hollow spaces below
- Underground collapse causes the surface above to crack and sink
- When both layers fail simultaneously, a breach forms — a hole from surface to underground that attackers can descend through
Siege Environmental Effects
Siege weapons can be used against terrain, not just units and buildings.
| Target terrain | Siege effect | Turns required | Result |
|---|---|---|---|
| Dense Forest | Burns/clears | 3 | Dense Forest → Sparse Forest → Cleared Land |
| Sparse Forest | Partial clearing | 2 | Sparse Forest → Cleared Land |
| Swamp | Disruption | 4 | Swamp → Mudflat (worse movement, less food) |
| Hills | Erosion | 6 | Hills → Damaged Plains (reduced defense bonus) |
| Mountain | Rockfall | 10+ | Mountain → Rocky Rubble (impassable patches) |
Scorched Earth consequence: Cleared land via siege does not immediately become farmland. It passes through a Scorched Earth state with unhappiness and local climate penalties before recovering. A player who carpet-bombs forests degrades their own agricultural base.
Dense Forest → Scorched Earth (0 yields, -happiness nearby)
→ Cleared Land (base yields only)
→ Engineer improves → Farmable Plains
Without Engineer:
Cleared Land → Scrubland (low yield, slow recovery)
Scrubland → decades → recovering sparse forest
Terrain Modification
Engineers and Demolitions Experts can reshape terrain permanently.
| Action | Who | Tech required | Time | Cost | Result |
|---|---|---|---|---|---|
| Flatten Hill | Demolitions Expert | Explosives | 6-8 turns | High materials | Hill → Plains |
| Level Cratered Terrain | Engineer | Masonry | 4-5 turns | Medium materials | Cratered → stable |
| Mountain Pass | Demolitions Expert | Deep Boring | 10-15 turns | Very high | Mountain → Pass tile (slow movement, reduced defense) |
| Mountain Tunnel | Demolitions Expert | Deep Boring + Tunnel Engineering | 12-18 turns | Extreme | Underground corridor through mountain range |
| Canal | Engineer | Hydraulics | 8-10 turns | High | Converts tile to navigable waterway |
| Levee | Engineer | Hydraulics | 4-6 turns | Medium | Raises low terrain, flood protection |
| Quarry Expansion | Engineer | Masonry | 3-4 turns | Low | Deepens quarry, +stone yield |
| Forest Clearance | Demolitions Expert | Explosives | 2 turns | Low materials | Forest → Cleared Land (controlled, minimal scorching) |
All terrain modifications are permanent. Flattening a hill cannot be undone. Mountain tunnels cannot be collapsed except by siege (see UNDERGROUND.md).
Tile Repair
| Repair method | Who | Cost | Time | Limit |
|---|---|---|---|---|
| Engineer on tile | Engineer unit | Materials | Slow | Up to Cratered |
| Mason Lodge queue | City production | Production | Medium | Up to Cratered |
| Natural recovery | Passive | Free | Very slow | Up to Damaged |
| Reinforcement | Engineer underground | Materials++ | Slow | Underground only |
Cannot be repaired: Full Sinkhole, Ruins. These are permanent terrain changes. A tile that has fully subsided remains a depression or void. Plan accordingly.