Add roadmap of agreed next features

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/ROADMAP.md

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+# Roadmap
+
+Agreed on 2026-11-05. Worked through in this order; every block is committed, pushed and deployed
+on its own. Details not listed here are decided along the way.
+
+## 1. Open items
+
+1. **Heroes attack every master** – with rival masters or several players, each hero wave marches
+   to the heart of the *strongest* living master (most creatures and gold), not only the player's.
+2. **Co-op campaign offline with an AI partner** – "League against the Lightwatch" playable
+   without the server: the partner is an allied AI master with its own dungeon (built like a
+   rival); its creatures join attacks and it sends gold when the player runs short.
+3. **Resume editor co-op runs** – an interrupted multiplayer run of an editor campaign goes on at
+   the reached mission; the host keeps the progress.
+4. **New screenshots** – title demo, language dropdown, co-op campaign.
+
+## 2. Bridges
+
+Stone bridges over lava exist already (75 gold per tile).
+
+1. **Wooden bridges burn** – fire spells, fire traps and dragon fire set them alight; after a few
+   seconds they collapse and units on them fall into the water. Stone bridges are fireproof.
+2. **Drawbridge** – an expensive bridge (about 150 gold per tile) with a per-bridge switch:
+   *manual* (a click raises or lowers the whole bridge) or *automatic* (rises when heroes come
+   near, lowers afterwards). Knights can only tear it down while it is lowered.
+3. **Cooling lava** – frost spells and frost traps turn lava into walkable obsidian for a while.
+4. **Repairing bridges** – imps repair damaged bridges; knights wear bridges down step by step
+   instead of in one blow.
+
+## 3. The surface world
+
+1. **Surface terrain** – grass, trees, paths, daylight and sky. Trees act like earth: imps fell
+   them.
+2. **Wood** – a second resource from felled trees. Wooden bridges, doors, siege engines and room
+   upgrades cost wood.
+3. **Fortresses above ground** – walls, towers, a gate, a clearing with torches.
+4. **Siege weapons** – heroes bring battering rams (against doors) and catapults (against towers);
+   the player builds his own siege engines in a workshop.
+5. **Missions** – the last mission of the main campaign (M30) and of the co-op campaign (M20) lead
+   to the surface: the dungeon half lies in the rock (gold and more), the other half is a forest
+   with the High Marshal's fortress to destroy. Free play and multiplayer get a map option
+   "Surface". The map editor gets the new terrain.
+
+## 4. Additions
+
+1. **Random events** – earthquake (tunnels cave in), lava eruption, flood, gold vein found. Rare
+   (every 8–12 minutes), free play and multiplayer only, can be switched off in the menu; in
+   campaigns only through new script blocks.
+2. **Creature abilities** – from level 5 every creature has an active ability (ogre stomp, spider
+   web, mage chain lightning, ...), used automatically and wisely, with a cooldown.
+3. **Bosses and elite heroes** – every 5th wave brings a boss hero with a health bar at the top,
+   an ability of its own and loot (gold, runes).
+4. **Wild beasts** – beasts in caves (cave bears, giant beetles, ...) that can be tamed in the
+   prison and become creatures.
+5. **Room upgrades** – rooms can be upgraded to level 2 and 3 for gold and wood (a library that
+   researches faster, ...), shown by ornaments and brighter light.
+6. **Creature equipment** – the forge makes weapons and armour in tiers (iron, steel, rune);
+   creatures fetch the best fitting piece themselves, the strongest first; equipment is visible.
+7. **Creature relationships** – creatures like or hate each other, quarrel, and work better with
+   friends; the lair shows who likes whom.
+8. **Dungeon visitors** – neutral traders and smugglers come through the portal and sell rare
+   traps, runes or creatures for gold.
+9. **Dynamic music** – procedural music that changes between calm and battle and swells when
+   heroes come.
+10. **Tutorial mission** – an interactive introduction with Crookfinger (digging, rooms,
+    creatures, traps), built with the editor and script blocks.
+11. **Statistics** – charts at the end of a game (gold over time, creatures, kills, buildings; for
+    every player in multiplayer) and lifetime totals in the profile.
+12. **Achievements** – 50+ achievements with pixel badges, including hidden and humorous ones in
+    Crookfinger's style and progress bars, stored per user on the server.
+13. **Seasonal events** – cosmetic touches by date (pumpkins at Halloween, snow on the surface in
+    winter, ...).