diff --git a/docs/PROGRESSION_DESIGN.md b/docs/PROGRESSION_DESIGN.md
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+# Progression and challenges design
+
+Status: **proposal**. Nothing here is built yet.
+
+Today the island runs out of goals after a few days: once you have stone
+tools, a hut, a bow and a fire, the only threats are wolves at night, the
+cold and your diet. This plan adds a **second tier of materials** (iron and
+cut stone) that makes you go somewhere risky to get them, and **new
+adversaries and hazards** that grow over the days, so there's always a next
+thing to build toward and a reason to.
+
+All content stays procedural or CC0, data-driven (`data/items.json`,
+`data/recipes.json`, new `data/creatures.json`), and runs through Actions,
+so it works on a server the same way everything else does after M2.4/M2.5.
+
+## 1. The progression in one picture
+```
+ stone tools ──> find iron (nuggets, rust-streaked boulders, the barrow)
+      │                    │
+      │           clay + stone ──> charcoal kiln, smelter
+      │                    │        (ore + charcoal -> iron bar, takes time and fuel)
+      │                    v
+      │                  forge ──> iron axe / pickaxe / spear / arrows,
+      │                    │        nails, hinges, lantern, cooking pot
+      │                    v
+      └──────────> stonecutter (needs iron) ──> stone walls, floors,
+                                                 pillars, stairs, hearth
+```
+Each step needs something from a harder, more dangerous part of the island,
+so progression and challenge pull on each other.
+
+## 2. Iron
+**Where it comes from:**
+- **Iron nuggets**: small ground pickups in the scree at the foot of the
+  mountain rim and in stream beds. A handful per day; enough for your first
+  bars, not for a base. (Regrow slowly, like flint.)
+- **Rust-streaked boulders**: a new resource node, red-brown streaks in the
+  rock, mostly high on the rim slopes and around the wolf den. Needs a stone
+  pickaxe; gives stone plus 2-4 iron ore. These are the main supply.
+- **The barrow** (§4): iron scrap and a few ready bars inside, guarded.
+
+**Clay** (new): lumps on the lake shore and in the shallows, picked by hand.
+
+**Processing** (all new pieces, placed like a campfire, state on the server):
+| Piece | Recipe | Does |
+|---|---|---|
+| Charcoal kiln | 10 stone, 6 clay | wood in, charcoal out (1 per 2 wood, 30 s each) |
+| Smelter | 15 stone, 10 clay, 2 iron nuggets | iron ore or 3 nuggets + 1 charcoal -> 1 iron bar (45 s); burns charcoal, goes out in heavy rain without a roof |
+| Forge (anvil + hearth) | 6 iron bars, 10 stone, 4 wood | the station for iron recipes |
+
+Smelting **takes real time** and the smelter keeps working while you're
+away (like a campfire burning), so you load it, go and do something else,
+and come back. On a server everyone can see the glow and use it.
+
+**What iron makes** (at the forge):
+| Item | Recipe | Why you want it |
+|---|---|---|
+| Iron Axe | 2 iron, 2 wood | tier 2: fells trees in half the hits, better weapon (14) |
+| Iron Pickaxe | 3 iron, 2 wood | tier 2: mines rust boulders fast, and **granite** outcrops (cut stone) |
+| Iron Spear | 2 iron, 3 wood | 26 damage, 40 thrown |
+| Iron Arrows x10 | 1 iron, 4 sticks, 4 feathers | +50% damage |
+| Nails x10 | 1 iron | building upgrades (below) |
+| Iron Lantern | 2 iron, 1 resin | hands-free light you hang on a wall or carry; wolves hesitate like a torch, rain doesn't put it out |
+| Cooking Pot | 3 iron | placed over a fire: **stews** that count for two diet groups at once (e.g. meat + greens), so a balanced diet is easier once you've earned it |
+| Iron-banded Door | 2 iron, 4 wood, nails | strong door (wolves, later raiders, can't break it) |
+| Iron armour (later) | bars + hide | damage reduction; heavy, slows stamina regen |
+
+**Tool durability** (new, recommended): tools and weapons wear with use and
+break (stone ~60 uses, iron ~200). Repair at a workbench (stone) or forge
+(iron) for a little material. This is what makes iron worth getting rather
+than a nice-to-have, and keeps you coming back to the forge.
+
+## 3. Stone building
+**Cut stone** comes from granite outcrops (iron pickaxe) or from cutting
+ordinary stone at a **stonecutter** (8 wood, 4 iron, 10 stone).
+
+New pieces (same 2 m grid, snap with the wood ones):
+| Piece | Recipe | Notes |
+|---|---|---|
+| Stone floor | 4 cut stone | |
+| Stone wall | 6 cut stone | |
+| Stone pillar | 3 cut stone | carries load: resets support for what's on top |
+| Stone stairs | 4 cut stone | first real stairs (also a wooden version) |
+| Stone hearth | 10 cut stone | an indoor fire: heat in a radius 1.5x a campfire's, never rained out, cooks |
+| Arch / doorway | 6 cut stone | takes a wood or iron door |
+
+**Support rules:** stone that touches the ground has support 1 and loses
+only 5% going up, so you can build tall stone towers and use **stone at the
+bottom, wood on top** (Valheim style). Wood can't hold stone up: a stone
+piece on a wooden one has no support. Stone pillars inside a wooden hall
+let it span further. Interior walls and doors work as they do now.
+
+**Why bother:** stone is sturdier (§4: things that break walls can't break
+stone), it's warmer (a stone room counts as better shelter, a little extra
+warmth), it doesn't burn (§5, lightning), and it lets you build big.
+
+**Wooden upgrades** too, using nails: windows (light, still sheltered),
+wooden stairs, fences and a **palisade wall + gate** (a ring round your base,
+taller than a wolf can jump).
+
+## 4. Adversaries
+Each one is a different kind of problem, not just more HP.
+| Adversary | Where / when | What it does | What beats it | Drops |
+|---|---|---|---|---|
+| **Wolves** (today) | nights from day 4 | pack circles, darts in | fire, torch, walls | pelt |
+| **Alpha wolf** | every 7th night (the "wolf moon": the moon turns red, a big howl) | leads the pack, 3x HP, **breaks wooden doors** | iron door, stone walls, a fight with iron weapons | alpha pelt (warmest cloak), fang |
+| **Bear** | daytime, deep forest near the rim; one per island | wanders, sniffs out food: **raids unattended chests with food and campfires with meat** | a palisade, stone storage, or a hard fight (spears, arrows from cover) | big hide (rugs, warm bedding: better rest), fat (resin/lantern fuel), lots of meat |
+| **Barrow guards** | the **barrow**: an ancient burial mound with a stone ring, generated from the seed (like the den) | skeletal guards wake if you enter at night (or always after day 10); slow, hit hard, ignore torches | daylight raids, blunt weapons (club does +50% to bone) | iron scrap, a few iron bars, a **barrow key piece** (§6) |
+| **Crows / foxes** | anytime, near food | steal berries and raw meat left on the ground or in open fires | a closed chest | — |
+
+Creatures run on the server (needs M2.5's server-side creature framework),
+so on a server everyone faces the same bear and the same alpha.
+
+## 5. Hazards and pressure (not creatures)
+- **Food spoilage**: raw meat and fish rot after 2 in-game days (berries
+  3, mushrooms 4). A **smoking rack** (wood, fibre) and **salt** (from the
+  sea-cliff rocks) preserve them. Cooked food keeps longer. Makes storing
+  food a choice, and feeds the bear/crow raids.
+- **Food poisoning**: raw meat sometimes makes you sick (stamina regen
+  halved, can't eat for a minute). Cooking fixes it.
+- **Blizzards**: on cold days a blizzard can roll in: visibility drops,
+  warmth falls fast outside, snow piles on roofs. Being sheltered matters.
+- **Lightning**: in storms, lightning can strike tall things near the rim;
+  a struck tree or **wooden** piece catches fire and burns for a while
+  (stone doesn't). Optional (§8), as losing a base to weather can feel unfair.
+- **Hard winters**: every ~12 days, three cold days in a row (snow down to
+  the valley, the lake edge freezes, fewer animals). A seasonal goal: stock
+  food and fuel before it.
+
+## 6. Something to aim for: the Old Stag (optional boss)
+Three **barrow key pieces** (from barrow chests) open the **standing
+stones** on the rim. At night they summon the **Old Stag**, a huge antlered
+spirit: charges, summons a wolf pack, has phases. Beating it drops its
+antler: **antler pickaxe** (mines anything, even granite, fast) and a
+trophy. The world remembers it was beaten (a message on a server).
+
+It's a milestone, not a gate: nothing is locked behind it except bragging
+rights and the best pickaxe. More bosses can come with new worldlets.
+
+## 7. Phases and tests
+| Phase | Delivers | Done when |
+|---|---|---|
+| **P1 Iron** | nuggets, rust boulders, clay, charcoal kiln, smelter, forge, iron tools/weapons/arrows/nails/lantern/pot, durability and repair | a test smelts a bar from ore it mined and crafts an iron axe; the axe fells a tree in half the hits and wears out after ~200 uses |
+| **P2 Stone** | stonecutter, granite, stone pieces, stairs, pillars, hearth, stone-on-wood rule, windows, palisade | a stone tower 10 m high stands; stone on wood refuses; a hearth keeps a stone room Sheltered and Warm in a blizzard |
+| **P3 Adversaries** | alpha wolf + wolf moon, bear and food raids, crows/foxes, the barrow and its guards | the alpha breaks a wooden door but not an iron one; the bear empties an unguarded food chest and ignores one behind a palisade |
+| **P4 Hazards** | spoilage and preserving, food poisoning, blizzards, hard winters, (lightning) | meat rots on schedule and keeps on the rack; a blizzard drops warmth outdoors and not in a hearth room |
+| **P5 Boss** | key pieces, standing stones, the Old Stag | a scripted fight test reaches the end and drops the antler |
+
+**Order:** P1 and P2 are items, recipes and pieces through Actions, so they
+work online straight away and can come any time (before or after M2.5).
+P3 and P5 are creatures, so they should come **after M2.5**, built directly
+on the server-side creature code instead of being written twice. P4 can come
+any time; spoilage on a server runs with the shared clock.
+
+## 8. Questions for you
+1. **Durability:** tools wear out and need repairing (recommended: it's
+   what makes iron matter), or tools last forever?
+2. **Lightning and fire:** can storms set wooden buildings alight, or keep
+   weather from destroying bases?
+3. **Raids:** should adversaries damage buildings (the alpha breaking wooden
+   doors, the bear raiding chests), or only threaten the player?
+4. **The boss:** worth having (the Old Stag), or keep it to the wild
+   island with no boss fights?
+5. **Order:** P1 iron + P2 stone now, then M2.5, then the creatures? Or
+   M2.5 first?
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index f8cfdf1..c2cf682 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -37,6 +37,10 @@ Detailed plan in `docs/SURVIVAL_DESIGN.md` (phases M1a–M1d).
 - [x] Fishing (rod, perch and trout, grilling) and a mixed diet *(M1e)*
 - [ ] Hide armour, more recipes, sea fishing *(later M1 polish)*
 - [x] Wild flax (fibre plants) *(polish)*
+- [ ] **Iron, stone building and new adversaries**: iron nuggets and ore,
+      smelting and a forge, iron tools and durability, cut-stone building,
+      an alpha wolf, a bear, a barrow with guards, spoilage and blizzards
+      *(phases P1-P5, `docs/PROGRESSION_DESIGN.md`)*
 - [ ] **Tutorial world**: a guided first island that teaches gathering,
       crafting, chopping, food and the mixed diet, hunting, fishing,
       shelter and the night *(phases T1-T4, `docs/TUTORIAL_DESIGN.md`)*