A tunnel driven inside the hill. You come out where the enemy is not looking — and the hill above you stays intact.

You can tunnel a hill through, drop a ledge on someone's head, build a bridge or breach a dam and flood the low ground. A crater stays until the end of the battle, and the enemy sees it.
Ground is not a colour but a set of rules: what a blast turns into, where a ricochet goes, whether the slope will creep and what driving across costs.
| Ground | Crater | Blast | Driving | Ricochet | Foxhole | Why it matters |
|---|---|---|---|---|---|---|
| Earth | ×1 | ×1 | ◆1 | 0 % | yes | Ordinary ground: digs, crumbles, holds a foxhole. |
| Sand | ×1.6 | ×1 | ◆1 | 0 % | yes | The crater is half again as wide, and slopes creep under their own weight. |
| Rock | ×0.4 | ×1 | ◆1 | 72 % | no | Cannot be dug and gives no foxhole. It ricochets instead: nearly three quarters of shots glance off. |
| Ice | ×2.2 | ×1 | ◆1 | 25 % | yes | A crater more than twice as large, and the machine slides down the slope. The most dangerous footing there is. |
| Marsh | ×1.2 | ×0.5 | ◆2 | 0 % | yes | Damps a blast by half, but driving through costs two points instead of one. |
| Concrete | ×0.7 | ×1 | ◆1 | 35 % | no | Tougher than stone, no digging in. Built with Concrete from the arsenal. |
| Snow | ×0.9 | ×0.9 | ◆1 | 0 % | yes | Builds up in layers during snowfall, slides, and damps a blast a little. |
Terrain here is a weapon and a shelter at once. All of it costs action points and happens in plain sight of the enemy.
A tunnel driven inside the hill. You come out where the enemy is not looking — and the hill above you stays intact.
Every ledge has a support, and you can see it. Knock it out and the ledge comes down where the enemy stands.
Brings down every ledge on the map at once. The map after it is a different map.
Eats the ground for three turns running. A position that was excellent sinks under the enemy tracks.

Under the Tide arena rule the water rises every three turns, and the low ground goes first. A breached dam raises it at once and completely — along with whoever dug in there.
The reverse is true as well: Concrete from the arsenal builds a bridge across a gap — but only from the edge inward, you cannot hang a span in mid-air. And the enemy breaks that bridge with two hits, after which nobody crosses.
All six can be broken, and every one of them breaks in somebody's favour — not always yours.
Three hundred damage within 120 px and a chain reaction at 150: the hit travels farther than any shell radius.
Two hits and nobody crosses. Whoever breaks the bridge breaks it for themselves too.
Intact, it holds the water back. Breached, the low ground goes under — along with whoever dug in there.
Damps the wind by 30 % across a 190° sector. Knock it down and the enemy loses their zeroing.
Holds for six turns on its own, then falls with no shot fired. The clock runs for both of you.
Four per cent of your health a turn within 98 px. A position can be excellent and uninhabitable at once.

The enemy sees it exactly as you do — and both of you have to live with the map you have just remade.