Research in the library: rooms, spells, towers, traps and doors are discovered in a fixed order

- studying creatures collect research points (mages and owls best, higher levels faster); studying gives less mana than before
- free play starts with the basics; campaign missions know what their story allows and can research what the next four missions would bring
- research shown in the top bar; the library's info lists the current item and what comes next; locked tools say whether they can be researched

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

src/game.rs

@@ -462,6 +462,12 @@ pub struct Game {
     pub rollers: Vec<crate::traps::Roller>,
     #[serde(default)]
     pub clouds: Vec<crate::traps::Cloud>,
+    #[serde(default)]
+    pub known: Vec<bool>, // tools known (ui::TOOLS order; empty = old savegame: everything)
+    #[serde(default)]
+    pub researchable: Vec<bool>, // tools that can be researched in the library
+    #[serde(default)]
+    pub research: f32, // research points towards the current item
     #[serde(skip)]
     pub forge_work: f32, // work done in the forge this frame
     #[serde(skip)]
@@ -555,6 +561,7 @@ impl Game {
         g.wave_timer = FIRST_WAVE + ((dist - 45.0) * 1.5).clamp(0.0, 300.0);
         g.guard_treasures();
         g.place_dwarf_caves(seed);
+        g.init_research(None);
         g.msg("msg.welcome1", vec![]);
         g.msg("msg.welcome2", vec![]);
         g.msg("msg.welcome3", vec![]);
@@ -631,6 +638,9 @@ impl Game {
             rollers: Vec::new(),
             clouds: Vec::new(),
             forge_work: 0.0,
+            known: Vec::new(),
+            researchable: Vec::new(),
+            research: 0.0,
             parts: Vec::new(),
             stuck: Vec::new(),
             vrng: crate::particles::vrng(),
@@ -678,6 +688,9 @@ impl Game {
     }
 
     pub fn tool_allowed(&self, tool: usize) -> bool {
+        if !self.known.is_empty() {
+            return self.known(tool);
+        }
         self.mission.as_ref().map_or(true, |m| m.tools.get(tool).copied().unwrap_or(true))
     }
 
@@ -1069,6 +1082,7 @@ impl Game {
         self.update_units(dt);
         self.update_towers(dt);
         self.update_forge(dt);
+        self.update_research();
         if !self.rivals.is_empty() {
             self.update_rivals(dt);
         }
@@ -3063,7 +3077,14 @@ impl Game {
                 }
                 e.working = true;
                 let rate = if e.kind == EK::Mage { 1.2 } else { 0.5 };
-                self.mana = (self.mana + rate * dt).min(self.mana_max());
+                self.mana = (self.mana + rate * 0.5 * dt).min(self.mana_max());
+                // research: mages and owls are the scholars
+                let points = match e.kind {
+                    EK::Mage => 1.6,
+                    EK::Owl => 1.3,
+                    _ => 0.5,
+                } * (1.0 + 0.12 * (e.level - 1) as f32);
+                self.add_research(points * dt);
                 e.xp += 3.0 * dt;
                 e.timer -= dt;
                 if e.timer <= 0.0 {