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>

lang/de.lang

@@ -789,3 +789,11 @@ best.b.frost.text = Kälte macht Helden langsam, und langsame Helden sind leicht
 best.b.door_wood.text = Hält Zugluft und Ritter draußen - eine Weile.
 best.b.door_iron.text = Schwer, genietet, stur. Bringt einen Rammbock mit, Helden.
 best.b.door_magic.text = Schlag zu, und sie schlägt zurück. Verschlossen ist sie das Ende jedes Ganges.
+
+# research
+hud.research = Forschung
+research.now = Erforscht: {0} ({1}%)
+research.next = danach: {0}
+research.done = Hier gibt es nichts mehr zu erforschen.
+msg.researched = Erforscht: {0}! Jetzt im Baumenü.
+msg.tool_research = Noch nicht erforscht - Kreaturen in der Bibliothek arbeiten daran.

lang/en.lang

@@ -790,3 +790,11 @@ best.b.frost.text = Cold makes heroes slow, and slow heroes make easy targets.
 best.b.door_wood.text = Keeps the draught and the knights out - for a while.
 best.b.door_iron.text = Heavy, riveted, stubborn. Bring a battering ram, heroes.
 best.b.door_magic.text = Strike it and it strikes back. Locked, it is the end of every corridor.
+
+# research
+hud.research = Research
+research.now = Researching: {0} ({1}%)
+research.next = then: {0}
+research.done = Nothing left to research here.
+msg.researched = Researched: {0}! It is in the build menu now.
+msg.tool_research = Not researched yet - creatures studying in the library work on it.

src/campaign.rs

@@ -504,6 +504,7 @@ pub fn start_mission(i: usize, carry: Option<&Carry>) -> Game {
         g.add_rival(side, x, y, diff);
     }
     g.place_dwarf_caves(d.seed);
+    g.init_research(Some(i));
     let heart = d.gate || d.forts.iter().any(|f| f.heart);
     if !heart {
         g.gate_hp = 0.0;

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 {

src/main.rs

@@ -14,6 +14,7 @@ mod menu;
 mod platform;
 mod particles;
 mod props;
+mod research;
 mod rival;
 mod render3d;
 mod save;
@@ -862,7 +863,8 @@ async fn main() {
                     }
                     UiAction::OpenMenu => menu.page = Some(Page::Pause),
                     UiAction::Locked => {
-                        app.game.msg("msg.tool_locked", vec![]);
+                        let locked = ui.last_locked.unwrap_or(usize::MAX);
+                        app.game.msg(if app.game.can_research(locked) { "msg.tool_research" } else { "msg.tool_locked" }, vec![]);
                         app.game.sfx_ui(game::Sfx::Error);
                     }
                     UiAction::CloseHelp | UiAction::SelectLanguage(_) | UiAction::Consumed => {}

src/research.rs

@@ -0,0 +1,140 @@
+// Research: creatures studying in the library collect research points, and rooms, spells,
+// towers, traps and doors are discovered one after another in a fixed order. Free play starts
+// with the basics; a campaign mission knows what its story allows and may research what the
+// next few missions would bring.
+
+use crate::game::*;
+
+// what is researched, in this order: (index in ui::TOOLS, research points)
+pub const RESEARCH: &[(usize, f32)] = &[
+    (5, 200.0),   // training hall
+    (10, 250.0),  // heal
+    (21, 300.0),  // forge
+    (22, 250.0),  // spike pit
+    (29, 250.0),  // wooden door
+    (15, 400.0),  // cannon tower
+    (12, 450.0),  // torture chamber
+    (26, 300.0),  // alarm bell
+    (11, 500.0),  // summon
+    (13, 550.0),  // temple
+    (23, 500.0),  // poison vent
+    (30, 500.0),  // iron door
+    (18, 550.0),  // aerie
+    (16, 650.0),  // magic tower
+    (24, 650.0),  // fire jet
+    (25, 650.0),  // stone roller
+    (19, 700.0),  // steel walls
+    (28, 800.0),  // frost glow
+    (27, 900.0),  // rune mine
+    (31, 1100.0), // magic door
+];
+
+// known from the start in free play
+pub const BASE_TOOLS: &[usize] = &[0, 1, 2, 3, 4, 6, 7, 8, 9, 14, 17, 20];
+
+// campaign: what the next missions bring may be researched early
+const LOOKAHEAD: usize = 4;
+
+impl Game {
+    // free play (None) or campaign mission i: what is known, what can be researched
+    pub fn init_research(&mut self, mission: Option<usize>) {
+        let n = crate::ui::TOOLS.len();
+        match mission {
+            None => {
+                self.known = (0..n).map(|i| BASE_TOOLS.contains(&i)).collect();
+                self.researchable = vec![true; n];
+            }
+            Some(m) => {
+                let unlock = |i: usize| crate::campaign::TOOL_UNLOCK.get(i).copied().unwrap_or(0);
+                self.known = (0..n).map(|i| unlock(i) <= m).collect();
+                self.researchable = (0..n).map(|i| unlock(i) <= m + LOOKAHEAD && i != crate::game::RUNE_TOOL).collect();
+            }
+        }
+        self.research = 0.0;
+    }
+
+    pub fn known(&self, tool: usize) -> bool {
+        self.known.get(tool).copied().unwrap_or(true)
+    }
+
+    // the item being researched now: (index in RESEARCH)
+    pub fn research_target(&self) -> Option<usize> {
+        if self.known.is_empty() {
+            return None;
+        }
+        RESEARCH.iter().position(|&(t, _)| !self.known(t) && self.researchable.get(t).copied().unwrap_or(false))
+    }
+
+    // the next items after the current one (for the library's info)
+    pub fn research_queue(&self, n: usize) -> Vec<usize> {
+        RESEARCH.iter().enumerate().filter(|(_, &(t, _))| !self.known(t) && self.researchable.get(t).copied().unwrap_or(false)).map(|(k, _)| k).take(n).collect()
+    }
+
+    // could this tool still be researched (for the locked-tool message)?
+    pub fn can_research(&self, tool: usize) -> bool {
+        !self.known(tool) && self.researchable.get(tool).copied().unwrap_or(false) && RESEARCH.iter().any(|&(t, _)| t == tool)
+    }
+
+    pub(crate) fn add_research(&mut self, points: f32) {
+        if self.research_target().is_some() {
+            self.research += points;
+        }
+    }
+
+    pub(crate) fn update_research(&mut self) {
+        let Some(k) = self.research_target() else { return };
+        let (tool, cost) = RESEARCH[k];
+        if self.research >= cost {
+            self.research -= cost;
+            if let Some(v) = self.known.get_mut(tool) {
+                *v = true;
+            }
+            let name = crate::ui::tool_info(crate::ui::TOOLS[tool]).name;
+            self.msg("msg.researched", vec![name]);
+            self.sfx_ui(Sfx::LevelUp);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::map::*;
+
+    #[test]
+    fn studying_discovers_the_next_item() {
+        let mut g = Game::new(9, 64, 64);
+        assert!(!g.tool_allowed(5), "training hall must be researched");
+        assert!(g.tool_allowed(2) && g.tool_allowed(6));
+        let (cx, cy) = g.map.core;
+        for y in cy - 8..=cy - 5 {
+            for x in cx..=cx + 4 {
+                let t = &mut g.map.t[idx(x, y)];
+                t.kind = Kind::Library;
+                t.owner = Owner::Player;
+            }
+        }
+        g.recount();
+        for k in 0..4 {
+            g.spawn(EK::Mage, false, cx as f32 + 0.5 + k as f32, cy as f32 - 6.5, 3);
+        }
+        let mut found = false;
+        for _ in 0..(20 * 400) {
+            g.update(0.05);
+            if g.tool_allowed(5) {
+                found = true;
+                break;
+            }
+        }
+        assert!(found, "research points {}", g.research);
+    }
+
+    #[test]
+    fn missions_know_their_tools_and_research_ahead() {
+        let g = crate::campaign::start_mission(2, None);
+        assert!(g.tool_allowed(5), "training hall known from mission 3");
+        assert!(!g.tool_allowed(12));
+        assert!(g.can_research(10), "heal comes soon and can be researched");
+        assert!(!g.can_research(31), "magic doors are far away");
+    }
+}

src/rival.rs

@@ -85,6 +85,7 @@ impl Game {
         g.msg("msg.welcome1", vec![]);
         g.msg("msg.welcome2", vec![]);
         g.msg(if rivals == 0 { "msg.welcome_humans" } else if humans { "msg.welcome_both" } else { "msg.welcome_rivals" }, vec![rivals.to_string()]);
+        g.init_research(None);
         g.place_dwarf_caves(seed);
         g
     }

src/ui.rs

@@ -327,6 +327,7 @@ pub struct Ui {
     minimap_tex: Texture2D,
     minimap_t: f64,
     minimap_rect: Rect,
+    pub last_locked: Option<usize>, // the locked tool clicked last
     end_buttons: Vec<(Rect, u8)>,
     goals_rect: Rect, // mission goals panel (click: briefing) // end dialog: 0 new game, 1 next/again, 2 campaign
     lang_rects: Vec<(Rect, String)>,
@@ -378,6 +379,7 @@ impl Ui {
             minimap_tex: tex,
             minimap_t: -1.0,
             minimap_rect: Rect::new(0.0, 0.0, 0.0, 0.0),
+            last_locked: None,
             end_buttons: Vec::new(),
             goals_rect: Rect::new(0.0, 0.0, 0.0, 0.0),
             lang_rects: Vec::new(),
@@ -433,7 +435,10 @@ impl Ui {
                     self.open_cat = None;
                     UiAction::OpenMenu
                 }
-                TBtn::Tool(i) if !g.tool_allowed(i) => UiAction::Locked,
+                TBtn::Tool(i) if !g.tool_allowed(i) => {
+                    self.last_locked = Some(i);
+                    UiAction::Locked
+                }
                 TBtn::Tool(i) => {
                     self.open_cat = None;
                     self.tip = Some((i, get_time()));
@@ -442,6 +447,7 @@ impl Ui {
                 TBtn::Cat(c) => {
                     let tools = CATS[c].1;
                     if tools.len() == 1 && !g.tool_allowed(tools[0]) {
+                        self.last_locked = Some(tools[0]);
                         UiAction::Locked
                     } else if tools.len() == 1 {
                         self.open_cat = None;
@@ -518,6 +524,11 @@ impl Ui {
             let left = (limit - g.time).max(0.0);
             segs.insert(0, vec![txt(tr("hud.time_left"), if left < 120.0 { RED } else { GOLD }), Part::Gap, txt(mmss(left), TXT)]);
         }
+        if let Some(k) = g.research_target().filter(|_| g.counts[4] > 0) {
+            let (tool, cost) = crate::research::RESEARCH[k];
+            let name: String = tool_info(TOOLS[tool]).name.chars().take(18).collect();
+            segs.push(vec![txt(tr("hud.research"), BLUE), Part::Gap, txt(name, TXT), Part::Gap, Part::Bar(g.research / cost, BLUE)]);
+        }
         segs.push(vec![txt(tr("hud.payday"), if g.payday <= PAYDAY_WARN { RED } else { GOLD }), Part::Gap, txt(mmss(g.payday), TXT)]);
         segs.push(vec![txt(tr("hud.army"), TXT), Part::Gap, txt((g.army_value() as i32).to_string(), TXT)]);
         if !g.hand.is_empty() {
@@ -1215,6 +1226,21 @@ pub fn hover_info(g: &Game, ent: Option<usize>, tile: Option<(i32, i32)>) -> Vec
                 out.push((tr(ROOM_NAMES[r]), FRAME_HI));
                 match k {
                     Kind::Farm => out.push((trf("farm.food", &[(t.food as i32).to_string()]), GREEN)),
+                    Kind::Library => {
+                        let q = g.research_queue(4);
+                        if q.is_empty() {
+                            out.push((tr("research.done"), DIM));
+                        }
+                        for (n, k) in q.iter().enumerate() {
+                            let (tool, cost) = crate::research::RESEARCH[*k];
+                            let name = tool_info(TOOLS[tool]).name;
+                            if n == 0 {
+                                out.push((trf("research.now", &[name, ((g.research / cost * 100.0).min(99.0) as i32).to_string()]), BLUE));
+                            } else {
+                                out.push((trf("research.next", &[name]), DIM));
+                            }
+                        }
+                    }
                     Kind::Treasury if t.gold > 0 => {
                         let what = ["res.gold", "res.silver", "res.ruby", "res.diamond"][(t.res & 3) as usize];
                         out.push((trf("treasury.content", &[t.gold.to_string(), tr(what)]), GOLD));