concept iteration

docs/concept.md

@@ -33,14 +33,17 @@ Two sources feed the same production tree:
 - **Mining** — the player's starting resource method. Ores are extracted from the asteroid and smelted into basic materials.
 - **Scrap** — collected by dedicated salvage ships from destroyed enemy ships.
   - Scrap can be smelted into the same basic materials as mined ores.
-  - A dedicated **Reprocessing Plant** building can extract higher-level intermediate products from scrap (with randomised probabilities per product type), bypassing parts of the normal crafting chain.
+  - A dedicated **Reprocessing Plant** building can extract higher-level intermediate products from scrap (with fixed probabilities per product type), bypassing parts of the normal crafting chain.
 
 ## Ships & Shipyards
 
 - Shipyards are built at the edge of the asteroid.
 - When the player clicks a shipyard, they choose a blueprint from all currently unlocked blueprints.
 - The shipyard automatically produces one ship of the selected blueprint whenever all required materials are available in the shipyard.
-- Ships are fully autonomous: they travel to the right, engage enemy ships, and do not require player input.
+- Ships are fully autonomous and do not require player input. Known ship roles:
+  - **Combat ships** — travel right and engage enemy ships.
+  - **Salvage ships** — fly out to the battlefield, collect scrap from destroyed enemy ships, and return to the asteroid. They are vulnerable to enemy ships while operating.
+  - **Repair ships** — fly out and repair damaged player defence stations and other player ships in the field.
 - If the player's ships are all destroyed, enemy ships advance unhindered toward the player's defence stations and then the asteroid.
 
 ## Enemy Waves