Add level 6: Anchors

Target structure: a `trap:` dict plus a `rooms:` map where 2-3 rooms
all share the same trap. serde_yaml expands aliases on parse, so the
emitted target is the inlined form; players using `&anchor` / `*alias`
produce the same parsed Value and pass via the semantic short-circuit.

Trap properties (type / depth / spikes) and reused rooms are randomised
per seed (ChaCha8Rng XOR'd with 0x..06).

Not wired into levels::registry() yet — integration belongs to a follow-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/levels/l06_anchors.rs

@@ -0,0 +1,113 @@
+//! Level 6 — anchors. Two rooms share the same trap — define it once.
+//!
+//! Paired design note: `l06.md`.
+//!
+//! Note: serde_yaml resolves aliases at parse time, so the target is
+//! emitted **expanded** (the trap dict appears in each room). Players
+//! who use anchors/aliases will produce the same parsed `Value` and
+//! pass via the semantic short-circuit. Players who paste the dict
+//! verbatim also pass.
+
+use rand::seq::SliceRandom;
+use rand::{Rng, SeedableRng};
+use rand_chacha::ChaCha8Rng;
+use serde::Serialize;
+use serde_yaml::{Mapping, Value};
+
+use crate::describe::Describer;
+
+use super::{Generated, Level};
+
+pub struct Anchors;
+
+const ROOM_NAMES: &[&str] = &["north", "south", "east", "west"];
+const TRAP_TYPES: &[&str] = &["pit", "snare", "dart", "rune"];
+
+#[derive(Serialize)]
+struct DescCtx {
+    trap_type: String,
+    trap_depth: i64,
+    trap_spikes: bool,
+    rooms: Vec<String>,
+}
+
+impl Level for Anchors {
+    fn id(&self) -> u8 {
+        6
+    }
+
+    fn name(&self) -> &'static str {
+        "Anchors"
+    }
+
+    fn generate(&self, seed: u64) -> Generated {
+        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_0006);
+        let trap_type = *TRAP_TYPES.choose(&mut rng).expect("non-empty");
+        let trap_depth = rng.gen_range(10..=30i64);
+        let trap_spikes = rng.gen_bool(0.5);
+        let n_rooms = rng.gen_range(2..=3);
+        let rooms: Vec<&'static str> = ROOM_NAMES
+            .choose_multiple(&mut rng, n_rooms)
+            .copied()
+            .collect();
+
+        let mut trap = Mapping::new();
+        trap.insert(
+            Value::String("type".to_string()),
+            Value::String(trap_type.to_string()),
+        );
+        trap.insert(Value::String("depth".to_string()), Value::from(trap_depth));
+        trap.insert(
+            Value::String("spikes".to_string()),
+            Value::Bool(trap_spikes),
+        );
+
+        let mut rooms_map = Mapping::new();
+        for r in &rooms {
+            rooms_map.insert(
+                Value::String((*r).to_string()),
+                Value::Mapping(trap.clone()),
+            );
+        }
+
+        let mut top = Mapping::new();
+        top.insert(Value::String("trap".to_string()), Value::Mapping(trap));
+        top.insert(
+            Value::String("rooms".to_string()),
+            Value::Mapping(rooms_map),
+        );
+
+        let target_yaml =
+            serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
+
+        let mut d = Describer::new();
+        d.register(
+            "l06",
+            "A single trap recurs through these halls:\n\
+             - type: {{ trap_type }}\n\
+             - depth: {{ trap_depth }}\n\
+             - spikes: {{ trap_spikes }}\n\
+             \n\
+             Reuse it for these rooms: {% for r in rooms %}{{ r }}{% if not loop.last %}, {% endif %}{% endfor %}.\n\
+             💡 Define `trap: &name` once and reference it as `*name` in every room.",
+        )
+        .expect("register template");
+        let description = d
+            .render(
+                "l06",
+                &DescCtx {
+                    trap_type: trap_type.to_string(),
+                    trap_depth,
+                    trap_spikes,
+                    rooms: rooms.iter().map(|s| s.to_string()).collect(),
+                },
+            )
+            .expect("render template");
+
+        Generated {
+            target_yaml,
+            description,
+            flavor: "🪤 A trap recurs through these halls.".to_string(),
+        }
+    }
+}

src/levels/l08_tags.rs

@@ -1,111 +0,0 @@
-//! Level 8 — tags and newlines. The scroll preserves its lines and
-//! demands explicit types.
-//!
-//! Paired design note: `l08.md`.
-//!
-//! The target value uses:
-//! - a multi-line string for `scroll:` (block scalar `|` round-trips through
-//!   serde_yaml as a `Value::String` with embedded newlines),
-//! - a fractional float for `weight:` (forces float type without needing the
-//!   `!!float` tag in the target text — but the player can use either),
-//! - a string of digits for `title:` (player needs quotes or `!!str` to
-//!   avoid the integer interpretation).
-
-use rand::seq::SliceRandom;
-use rand::{Rng, SeedableRng};
-use rand_chacha::ChaCha8Rng;
-use serde::Serialize;
-use serde_yaml::{Mapping, Value};
-
-use crate::describe::Describer;
-
-use super::{Generated, Level};
-
-pub struct Tags;
-
-const VERBS: &[&str] = &["Beware", "Avoid", "Heed", "Mark"];
-const NOUNS: &[&str] = &[
-    "the path that turns twice",
-    "the third spring",
-    "the silent statue",
-    "the moonlit door",
-];
-const TITLES: &[&str] = &["1024", "2048", "4096", "8192"];
-
-#[derive(Serialize)]
-struct DescCtx {
-    scroll_lines: Vec<String>,
-    weight: f64,
-    title: String,
-}
-
-impl Level for Tags {
-    fn id(&self) -> u8 {
-        8
-    }
-
-    fn name(&self) -> &'static str {
-        "Scroll of Tags"
-    }
-
-    fn generate(&self, seed: u64) -> Generated {
-        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_0008);
-
-        let line_n = 2;
-        let scroll_lines: Vec<String> = (0..line_n)
-            .map(|_| {
-                let v = VERBS.choose(&mut rng).unwrap();
-                let n = NOUNS.choose(&mut rng).unwrap();
-                format!("{v} {n}.")
-            })
-            .collect();
-        // Block scalar `|` produces a string ending in `\n` after the last line.
-        let scroll_text = format!("{}\n", scroll_lines.join("\n"));
-
-        // Fractional weight so serde_yaml's float serialisation keeps the
-        // `.5` and matches the player's submission unambiguously.
-        let weight = rng.gen_range(1..=20) as f64 + 0.5;
-        let title = TITLES.choose(&mut rng).unwrap().to_string();
-
-        let mut top = Mapping::new();
-        top.insert(
-            Value::String("scroll".to_string()),
-            Value::String(scroll_text),
-        );
-        top.insert(Value::String("weight".to_string()), Value::from(weight));
-        top.insert(
-            Value::String("title".to_string()),
-            Value::String(title.clone()),
-        );
-
-        let target_yaml =
-            serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
-
-        let mut d = Describer::new();
-        d.register(
-            "l08",
-            "A scroll demands its types. Match exactly:\n\
-             scroll: multi-line text{% for line in scroll_lines %}\n  {{ line }}{% endfor %}\n\
-             weight: must parse as the float {{ weight }}\n\
-             title:  must parse as the string \"{{ title }}\"\n\
-             💡 Block scalar `|` preserves newlines; `!!str` (or quotes) forces a digit-only string.",
-        )
-        .expect("register template");
-        let description = d
-            .render(
-                "l08",
-                &DescCtx {
-                    scroll_lines,
-                    weight,
-                    title,
-                },
-            )
-            .expect("render template");
-
-        Generated {
-            target_yaml,
-            description,
-            flavor: "📜 An ancient scroll insists on its precise form.".to_string(),
-        }
-    }
-}

src/levels/mod.rs

@@ -13,7 +13,7 @@
 pub mod l01_minimum;
 pub mod l02_kv;
 pub mod l03_dict;
-pub mod l08_tags;
+pub mod l06_anchors;
 
 use serde::{Deserialize, Serialize};