Terrain & Environment

The three layers

Each hex is described by three independent layers, and any combination is possible:

Base terrain - the permanent ground type: plains, woodland, rock, water and the rest. Set when the map is generated and never changes on its own.
Weather - an environmental overlay like fog or a blizzard that sits on top of the terrain, the same kind across a region.
Battle damage - states the fighting itself creates: fire, rubble, flooding, scorched ground. These appear and spread during the battle.

On top of the three layers, individual hexes can also hold a ground item - a boulder, a wall, a debris field - placed at map generation or dropped by an ability. The four together decide what a hex costs to enter, how tall it stands for sightlines, how well you can see through it, and what hurts you for standing there.

How layers combine

The layers don't override one another - they stack, each by its own rule:

Property	How the layers combine
Height	Additive. Base elevation plus every layer's height bonus and any ground item. Taller terrain blocks more sightlines - and is also what blinds: height is visibility.
Move cost	Additive. The base terrain cost plus flat penalties from weather, damage and scatter - never less than 1 per hex.
Visibility	Height-driven. A layer's height obstruction blocks sightlines passing through the hex, and conceals any unit standing in it - raised cover and sunken defilade both hide. No separate visibility rating - the bigger the height swing, the blinder the hex.
Hazards	All apply. Every layer's hazard is active at once - a flooded hex in acid rain is both at the same time.

So a rocky hill (height) under fog (more height) churned into mud by rain (move cost) is all three at once. Move cost feeds your path budget in Movement & Positioning; the combined height feeds sightlines in Vision & Detection.

Base terrain

The ground type is the foundation every other layer builds on. The most common types and what they're worth:

Terrain	Cost	What it does
Open Plains	1 tile	Flat and fully exposed - no obstruction, no cover. The default ground.
Woodland	2 tiles	Canopy raises the hex height by 4 - it blocks sightlines through the hex and conceals anyone in it. The workhorse cover terrain.
Rocky Ground	1 tile	Raised stone (+2 height) gives cover against direct fire without slowing you.
Dust Flats / Snowfield	2 tiles	Sunken, low-profile ground (-2 height) - defilade that conceals a unit sitting in it, though it doesn't block sightlines passing over. Sensors also degrade across it.
Water	3 tiles	Very slow going, and it leaves you Wet - a soaked frame conducts, taking far more electrical damage and arcing its own power draw back through itself each turn. It does smother fire, though.
Ice Sheet	2 tiles	Slick footing - a unit standing on it loses a chunk of its effective mobility until it gets back onto solid ground.
Thermal Vent	2 tiles	Geothermal blaze sets units alight - you take a stacking burn each turn you linger, so don't.

Slow ground is often safe ground

The terrain that costs the most to cross is usually the terrain that hides and shields you. Woodland is twice the move cost of plains, but it raises you over sightlines and breaks line of sight - frequently worth the extra MP.

Weather

Weather drapes over whole stretches of the map, modifying every hex it touches without changing the terrain underneath. Its main currency is blindness - most weather cuts how far anyone can see:

Weather	Effect
Dense Fog	A tall obscuring bank (+4 height) - sightlines through it collapse to close range, and units inside it are concealed.
Heavy Rain	Light obstruction (+2 height), +1 move cost as terrain turns to mud, and it leaves units in it Wet - the same soaking water gives, so electrical fire bites much harder.
Blizzard	Whiteout (+4 height), +2 move cost, and cold that saps the mobility of anything caught in it.
Sandstorm	Abrasive obstruction (+3 height), +1 move cost, and grit that fouls optics - units inside it shoot less accurately.
Acid Rain	Light obstruction (+2 height) plus a corrosive hazard that eats unshielded armor - biting each unit that starts its turn in it or moves through it.
Resonance Storm	Light obstruction (+2 height), +1 move cost, and a destabilizing hazard that deals 10 armor-ignoring structure to every component plus a heavy stability jolt each round. Seeded by the Chorus Tempest Chorale.

Weather cuts both ways: it hides your advance as readily as the enemy's. A force built to fight at close range - or one carrying its own sensors - shrugs off a fog that cripples a sniper line. How a hex's height blocks and conceals sight is in Vision & Detection.

Battle damage

Unlike terrain and weather, battle damage is created by the fight. Explosions, incendiary weapons and terrain-shaping abilities stamp persistent states onto hexes mid-battle, reshaping the map as the engagement wears on:

State	Effect
Fire	Billowing smoke raises the hex height (+3) - blocking sightlines and concealing anyone in it - plus +2 move cost. A unit that starts its turn in it, or moves through it, catches fire and takes burning damage. After two rounds the blaze burns out into scorched ground.
Rubble	Collapsed debris raises the hex (+2 height) for fresh cover, at +1 move cost.
Flooded	+2 move cost and a flood hazard to lower systems.
Scorched Ground	Residual heat that lightly stresses occupying units for a few rounds before cooling.
EMP Zone	Residual interference - a unit lingering inside has its sensors and targeting degraded each round.

Most battle damage is laid by the fighting itself. Incendiary and plasma blast weapons set the ground on fire wherever they strike - each affected hex has a chance to ignite, and the Immolator Artillery is built to blanket whole tiles in flame. A fire spreads its smoke and heat for two rounds, then decays to scorched ground, which itself cools away a few rounds later. Plasma-trail and terrain-melting weapons leave the same trail of fire behind them.

Hazard tiles - fire, acid rain, geothermal vents and the rest - bite when a unit starts its turn standing in one, and again for every hazard hex it moves through during that turn. Racing a unit across a lane of fire is no longer free: it catches every tile it crosses. A hex seeded under a unit does no damage the instant it appears, though - the occupant pays for it at the start of its next turn, so there is a beat to move clear.

Battle damage means the terrain you deployed onto is not the terrain you'll be fighting over ten rounds later. A lane that was open plains can become a wall of fire; a cleared field can fill with rubble cover. Battle damage and weather stack independently - a hex can be both flooded and on fire, or burning under acid rain, and every layer's hazard bites at once. The effects these states inflict are resolved through How Damage Works and Status Effects.

Ground scatter

Maps are seeded with ground items - discrete obstacles sitting on individual hexes. They change a hex in two ways: how much it costs to enter, and whether you can stop there at all.

Item	Effect on the hex
Debris Field	+1 move cost; you can still path through and stop here.
Small Boulder	Raises height (+1) and costs +2 to cross - and you can't stop on it, only path through.
Large Boulder	Impassable. Blocks movement entirely and stands +2 tall, breaking line of sight.
Wall Segment	Impassable and +3 tall - a hard sightline blocker to route around.

Most scatter is destructible - boulders and walls have structure and armor, so a heavy enough weapon can blast a gap through an impassable line. Abilities place their own items too: Deploy Mine hides a trap on a hex, Drop Beacon plants a signal beacon, and a felled obstacle leaves the lane open behind it.

Elevation & height

Every hex has a base elevation, and each layer adds to it. The total is the hex's effective height, and it drives two systems at once:

Sightlines. A tall hex - whether from raw elevation, a forest canopy, or a wall on it - blocks line of sight across it and the hexes behind it. Standing on high ground lets you see and shoot over what would hide you on the flat. See Vision & Detection.
Climbing. Stepping up more than your frame's climb height is impossible, and dropping off a tall ledge is a crash descent that costs extra MP and damages you on landing. The movement side of height is in Elevation & climbing.

Because height is additive, layers compound: a rocky rise under woodland stands far taller than either alone. Reading the heights around you is how you find the firing positions that see out without being seen into.

Reshaping the ground

Terrain isn't fixed scenery - some abilities edit the map directly. Raise Terrain pushes a hex up to build instant cover or a firing platform; Resonance Quake drops terrain across an area to deny a lane or strand a unit on a ledge. Used well, you can manufacture the high ground rather than march to it.

The counter is Terrain Anchor: it roots the hex an Icaroid stands on so terrain-shaping can't raise or lower its elevation out from under it. An anchored unit keeps its footing and its sightline no matter how the enemy tries to reshape the ground - it locks the tile, not the frame, so it doesn't stop the unit being shot, only being terraformed.

Putting it together

Read a hex by its layers: the base ground sets the floor, weather and battle damage pile penalties and blindness on top, scatter blocks or slows it, and the heights all around decide who can see whom. Height adds - and height is what blinds - move cost adds, and every hazard bites at once. Pick paths and firing positions that turn the terrain to your advantage - cover and high ground that Movement & Positioning lets you reach and Vision & Detection lets you exploit.