Few explanations how the game works

`shapes:` list defines 2-3 polygons (name + sides + interior angle sum);
`copies:` is a list of 3-4 selections (with possible repetition) drawn
from the same pool. serde_yaml expands aliases on parse, so the target
is the inlined form; players using `- &name` anchors inside the list
and `*name` aliases in `copies:` produce the same Value and pass via
the semantic short-circuit.

All randomised per seed (ChaCha8Rng XOR'd with 0x..0B).

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

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

README.md

@@ -2,8 +2,15 @@
 
 A text dungeon game that teaches you YAML.
 
+The game uses actual YAML parsing libraries and generates semi-random levels
+by describing a secret YAML file that the user has to recreate in the editor.
+
+There are 11 levels in the game, so if you're on level 12, you won the game!
+
 ![screenshot](screenshot.png)
 
 ## How to start:
 
     cargo run
+
+## Dependencies

src/levels/l07_complex.rs

@@ -112,14 +112,16 @@ impl Level for Complex {
             serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
 
         let mut d = Describer::new();
+        // No tab characters: ratatui's Paragraph renders tabs unevenly,
+        // which combined with the typewriter's progressive reveal can
+        // produce overlapping characters. Use plain spaces for indents.
         d.register(
             "l07",
-            "Floor {{ floor }}.\n\
-             {% for r in rooms %}\n\
-             {{ r.name }} — a {{ r.kind }} (locked: {{ r.locked }})\n\
-             \texits:    {% for e in r.exits %}{{ e }}{% if not loop.last %}, {% endif %}{% endfor %}\n\
-             \tcontents: {% for c in r.contents %}{{ c }}{% if not loop.last %}, {% endif %}{% endfor %}\n\
-             {% endfor %}\n\
+            "Floor {{ floor }}.\n\n\
+             {% for r in rooms %}{{ r.name }} — a {{ r.kind }} (locked: {{ r.locked }})\n\
+               exits:    {% for e in r.exits %}{{ e }}{% if not loop.last %}, {% endif %}{% endfor %}\n\
+               contents: {% for c in r.contents %}{{ c }}{% if not loop.last %}, {% endif %}{% endfor %}\n\n\
+             {% endfor %}\
              💡 Combine maps, lists, and scalars — `floor:` is an int, each room is a dict with two lists.",
         )
         .expect("register template");

src/levels/l09_operators.rs

@@ -0,0 +1,135 @@
+//! Level 9 — special operators. The merge key (`<<`) lets a door
+//! inherit a template and override one field.
+//!
+//! Paired design note: `l09.md`.
+//!
+//! `serde_yaml` treats `<<` as a literal mapping key (it does NOT
+//! perform YAML 1.1 merge-key resolution). The target therefore carries
+//! a `<<` key whose value is the defaults dict, exactly as the player's
+//! `<<: *defaults` parses.
+
+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 Operators;
+
+const MATERIALS: &[&str] = &["oak", "iron", "stone", "silver", "bone"];
+
+#[derive(Serialize)]
+struct DescCtx {
+    default_material: String,
+    default_locked: bool,
+    north_locked: bool,
+    south_material: String,
+}
+
+impl Level for Operators {
+    fn id(&self) -> u8 {
+        9
+    }
+
+    fn name(&self) -> &'static str {
+        "Merge Keys"
+    }
+
+    fn generate(&self, seed: u64) -> Generated {
+        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_0009);
+        let default_material = (*MATERIALS.choose(&mut rng).unwrap()).to_string();
+        let default_locked = rng.gen_bool(0.5);
+        // The north door overrides locked; choose the opposite so the
+        // override is meaningful.
+        let north_locked = !default_locked;
+        // The south door overrides material; pick anything but default.
+        let other_materials: Vec<&str> = MATERIALS
+            .iter()
+            .filter(|m| **m != default_material)
+            .copied()
+            .collect();
+        let south_material = (*other_materials.choose(&mut rng).unwrap()).to_string();
+
+        // Build the defaults mapping (referenced by all doors).
+        let mut defaults = Mapping::new();
+        defaults.insert(
+            Value::String("material".to_string()),
+            Value::String(default_material.clone()),
+        );
+        defaults.insert(
+            Value::String("locked".to_string()),
+            Value::Bool(default_locked),
+        );
+
+        let mut north_door = Mapping::new();
+        north_door.insert(
+            Value::String("<<".to_string()),
+            Value::Mapping(defaults.clone()),
+        );
+        north_door.insert(
+            Value::String("locked".to_string()),
+            Value::Bool(north_locked),
+        );
+
+        let mut south_door = Mapping::new();
+        south_door.insert(
+            Value::String("<<".to_string()),
+            Value::Mapping(defaults.clone()),
+        );
+        south_door.insert(
+            Value::String("material".to_string()),
+            Value::String(south_material.clone()),
+        );
+
+        let mut top = Mapping::new();
+        top.insert(
+            Value::String("door_defaults".to_string()),
+            Value::Mapping(defaults),
+        );
+        top.insert(
+            Value::String("north_door".to_string()),
+            Value::Mapping(north_door),
+        );
+        top.insert(
+            Value::String("south_door".to_string()),
+            Value::Mapping(south_door),
+        );
+
+        let target_yaml =
+            serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
+
+        let mut d = Describer::new();
+        d.register(
+            "l09",
+            "Two doors share a template:\n\
+             default material: {{ default_material }}\n\
+             default locked:   {{ default_locked }}\n\
+             \n\
+             north_door overrides locked → {{ north_locked }}\n\
+             south_door overrides material → {{ south_material }}\n\
+             💡 Anchor the defaults (`door_defaults: &name`) and merge with `<<: *name` in each door.",
+        )
+        .expect("register template");
+        let description = d
+            .render(
+                "l09",
+                &DescCtx {
+                    default_material,
+                    default_locked,
+                    north_locked,
+                    south_material,
+                },
+            )
+            .expect("render template");
+
+        Generated {
+            target_yaml,
+            description,
+            flavor: "🚪 Two doors echo a single template.".to_string(),
+        }
+    }
+}

src/levels/l10_dynamic.rs

@@ -0,0 +1,101 @@
+//! Level 10 — dynamic values. The vault ledger accepts numbers and
+//! dates in many forms.
+//!
+//! Paired design note: `l10.md`.
+//!
+//! The target is canonical (decimal ints, decimal float, ISO date
+//! string). The lesson is that the player can write equivalent values
+//! in hex / octal / exponent forms — all parse to the same number.
+
+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 Dynamic;
+
+#[derive(Serialize)]
+struct DescCtx {
+    gold_dec: i64,
+    gold_hex: String,
+    silver_dec: i64,
+    silver_oct: String,
+    experience: f64,
+    date: String,
+}
+
+impl Level for Dynamic {
+    fn id(&self) -> u8 {
+        10
+    }
+
+    fn name(&self) -> &'static str {
+        "Vault Ledger"
+    }
+
+    fn generate(&self, seed: u64) -> Generated {
+        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_000A);
+
+        let gold = rng.gen_range(0x100..=0xFFFi64);
+        let silver = rng.gen_range(0o100..=0o777i64);
+        // Fractional float so the canonical serialisation keeps the `.5`.
+        let experience = rng.gen_range(10..=99) as f64 + 0.5;
+        let year = rng.gen_range(1100..=2050i64);
+        let month = rng.gen_range(1..=12i64);
+        let day = rng.gen_range(1..=28i64);
+        let date = format!("{year:04}-{month:02}-{day:02}");
+
+        let mut vault = Mapping::new();
+        vault.insert(Value::String("gold".to_string()), Value::from(gold));
+        vault.insert(Value::String("silver".to_string()), Value::from(silver));
+        vault.insert(
+            Value::String("experience".to_string()),
+            Value::from(experience),
+        );
+        vault.insert(
+            Value::String("date".to_string()),
+            Value::String(date.clone()),
+        );
+
+        let mut top = Mapping::new();
+        top.insert(Value::String("vault".to_string()), Value::Mapping(vault));
+
+        let target_yaml =
+            serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
+
+        let mut d = Describer::new();
+        d.register(
+            "l10",
+            "The vault ledger demands its values:\n\
+             gold:       {{ gold_dec }}   (try hex: 0x{{ gold_hex }})\n\
+             silver:     {{ silver_dec }} (try octal: 0o{{ silver_oct }})\n\
+             experience: {{ experience }} (any equivalent float form passes)\n\
+             date:       {{ date }}        (an ISO-8601 date string)\n\
+             💡 Any equivalent numeric form passes — what matters is the parsed value.",
+        )
+        .expect("register template");
+        let description = d
+            .render(
+                "l10",
+                &DescCtx {
+                    gold_dec: gold,
+                    gold_hex: format!("{:X}", gold),
+                    silver_dec: silver,
+                    silver_oct: format!("{:o}", silver),
+                    experience,
+                    date,
+                },
+            )
+            .expect("render template");
+
+        Generated {
+            target_yaml,
+            description,
+            flavor: "🪙 A vault ledger awaits in many ciphers.".to_string(),
+        }
+    }
+}

src/levels/l11_adv_anchors.rs

@@ -0,0 +1,141 @@
+//! Level 11 — advanced anchors. Anchor shapes inside a list, alias
+//! them elsewhere.
+//!
+//! Paired design note: `l11.md`.
+//!
+//! Like L6, serde_yaml expands aliases on parse, so the emitted target
+//! is the fully-inlined form. Players who use `&anchor` / `*alias`
+//! produce the same `Value` and pass via the semantic short-circuit.
+
+use rand::seq::SliceRandom;
+use rand::{Rng, SeedableRng};
+use rand_chacha::ChaCha8Rng;
+use serde::Serialize;
+use serde_yaml::{Mapping, Sequence, Value};
+
+use crate::describe::Describer;
+
+use super::{Generated, Level};
+
+pub struct AdvAnchors;
+
+const SHAPES: &[(&str, i64)] = &[
+    ("triangle", 3),
+    ("square", 4),
+    ("pentagon", 5),
+    ("hexagon", 6),
+    ("heptagon", 7),
+    ("octagon", 8),
+];
+
+#[derive(Serialize)]
+struct DescCtx {
+    shapes: Vec<ShapeDesc>,
+    copies: Vec<String>,
+}
+
+#[derive(Serialize)]
+struct ShapeDesc {
+    name: String,
+    sides: i64,
+    interior_angle_sum: i64,
+}
+
+fn shape_value(name: &str, sides: i64) -> Value {
+    let mut m = Mapping::new();
+    m.insert(
+        Value::String("name".to_string()),
+        Value::String(name.to_string()),
+    );
+    m.insert(Value::String("sides".to_string()), Value::from(sides));
+    m.insert(
+        Value::String("interior".to_string()),
+        Value::from((sides - 2) * 180),
+    );
+    Value::Mapping(m)
+}
+
+impl Level for AdvAnchors {
+    fn id(&self) -> u8 {
+        11
+    }
+
+    fn name(&self) -> &'static str {
+        "Advanced Anchors"
+    }
+
+    fn generate(&self, seed: u64) -> Generated {
+        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_000B);
+
+        let n = rng.gen_range(2..=3);
+        let picked: Vec<(&'static str, i64)> = SHAPES
+            .choose_multiple(&mut rng, n)
+            .copied()
+            .collect();
+
+        // The defining `shapes:` list.
+        let shapes_seq: Sequence = picked
+            .iter()
+            .map(|(name, sides)| shape_value(name, *sides))
+            .collect();
+
+        // `copies:` — random selections with possible repetition.
+        let m = rng.gen_range(3..=4);
+        let mut copies_seq = Sequence::new();
+        let mut copy_names = Vec::new();
+        for _ in 0..m {
+            let (name, sides) = picked.choose(&mut rng).unwrap();
+            copies_seq.push(shape_value(name, *sides));
+            copy_names.push((*name).to_string());
+        }
+
+        let mut top = Mapping::new();
+        top.insert(
+            Value::String("shapes".to_string()),
+            Value::Sequence(shapes_seq),
+        );
+        top.insert(
+            Value::String("copies".to_string()),
+            Value::Sequence(copies_seq),
+        );
+
+        let target_yaml =
+            serde_yaml::to_string(&Value::Mapping(top)).expect("serialise mapping");
+
+        let shape_descs: Vec<ShapeDesc> = picked
+            .iter()
+            .map(|(name, sides)| ShapeDesc {
+                name: (*name).to_string(),
+                sides: *sides,
+                interior_angle_sum: (sides - 2) * 180,
+            })
+            .collect();
+
+        let mut d = Describer::new();
+        d.register(
+            "l11",
+            "Shapes are defined once and reused.\n\
+             Definitions:\n\
+             {% for s in shapes %}- {{ s.name }}: sides={{ s.sides }}, interior={{ s.interior_angle_sum }}\n\
+             {% endfor %}\n\
+             Copies, in order: {% for c in copies %}{{ c }}{% if not loop.last %}, {% endif %}{% endfor %}\n\
+             💡 Anchor each shape in the list with `- &name`, then alias by `*name` in copies.",
+        )
+        .expect("register template");
+        let description = d
+            .render(
+                "l11",
+                &DescCtx {
+                    shapes: shape_descs,
+                    copies: copy_names,
+                },
+            )
+            .expect("render template");
+
+        Generated {
+            target_yaml,
+            description,
+            flavor: "🔺 The geometry chamber repeats its forms.".to_string(),
+        }
+    }
+}

src/levels/mod.rs

@@ -18,6 +18,9 @@ pub mod l05_dict_list;
 pub mod l06_anchors;
 pub mod l07_complex;
 pub mod l08_tags;
+pub mod l09_operators;
+pub mod l10_dynamic;
+pub mod l11_adv_anchors;
 
 use serde::{Deserialize, Serialize};
 
@@ -90,5 +93,11 @@ pub fn registry() -> Vec<Box<dyn Level>> {
         Box::new(l03_dict::Dict),
         Box::new(l04_list::List),
         Box::new(l05_dict_list::DictList),
+        Box::new(l06_anchors::Anchors),
+        Box::new(l07_complex::Complex),
+        Box::new(l08_tags::Tags),
+        Box::new(l09_operators::Operators),
+        Box::new(l10_dynamic::Dynamic),
+        Box::new(l11_adv_anchors::AdvAnchors),
     ]
 }

src/lib.rs

@@ -81,50 +81,246 @@ mod smoke {
         assert_eq!(loaded.current_seed, p.current_seed);
     }
 
-    #[test]
-    fn levels_generate_canonical_yaml() {
-        let registry = levels::registry();
-        assert_eq!(registry.len(), 3);
+    // ---- Per-level tests --------------------------------------------
+    //
+    // One test per level. `checked_level` runs the invariants every
+    // level must satisfy (correct id, valid & deterministic canonical
+    // YAML, self-similarity 1.0); each test then pins the *shape* its
+    // design note promises and, where it is the whole lesson, the
+    // semantic forgiveness.
 
-        // Level 1: any null-equivalent passes via the semantic short-circuit.
-        let g1 = registry[0].generate(0);
-        let parsed: serde_yaml::Value = serde_yaml::from_str(&g1.target_yaml).unwrap();
-        assert!(parsed.is_null());
+    /// Look up a string key in a YAML mapping, panicking with a clear
+    /// message if it is missing — keeps the per-level assertions terse.
+    fn field<'a>(v: &'a Value, key: &str) -> &'a Value {
+        v.get(key)
+            .unwrap_or_else(|| panic!("expected key `{key}` in {v:?}"))
+    }
+
+    /// Parse a target YAML string, asserting it is well-formed.
+    fn parse(yaml: &str) -> Value {
+        serde_yaml::from_str(yaml).expect("target is valid YAML")
+    }
+
+    /// Generate level `index` (0-based) with `seed`, assert the invariants
+    /// every level must satisfy, and return its output for shape checks:
+    /// - the level reports `id == index + 1`,
+    /// - the target is valid YAML,
+    /// - generation is deterministic for a given seed,
+    /// - the canonical target scores 1.0 against itself.
+    fn checked_level(index: usize, seed: u64) -> levels::Generated {
+        let registry = levels::registry();
+        let level = &registry[index];
+        let want_id = index as u8 + 1;
         assert_eq!(
-            similarity::semantic_or_textual(&g1.target_yaml, "---"),
+            level.id(),
+            want_id,
+            "registry index {index} must hold level {want_id}"
+        );
+
+        let g = level.generate(seed);
+        serde_yaml::from_str::<Value>(&g.target_yaml)
+            .unwrap_or_else(|e| panic!("level {want_id} target is not valid YAML: {e}"));
+
+        let again = level.generate(seed);
+        assert_eq!(
+            g.target_yaml, again.target_yaml,
+            "level {want_id} must be deterministic for a given seed"
+        );
+
+        assert_eq!(
+            similarity::semantic_or_textual(&g.target_yaml, &g.target_yaml),
+            1.0,
+            "level {want_id} target must score 1.0 against itself"
+        );
+        g
+    }
+
+    #[test]
+    fn registry_lists_all_eleven_levels() {
+        assert_eq!(
+            levels::registry().len(),
+            11,
+            "all 11 levels must be registered"
+        );
+    }
+
+    #[test]
+    fn level_01_minimum_is_a_null_document() {
+        // Any null-equivalent passes via the semantic short-circuit.
+        let g = checked_level(0, 0);
+        assert!(parse(&g.target_yaml).is_null(), "the minimum YAML is null");
+        assert_eq!(
+            similarity::semantic_or_textual(&g.target_yaml, "---"),
             1.0,
             "`---` should be accepted as the minimum YAML"
         );
         assert_eq!(
-            similarity::semantic_or_textual(&g1.target_yaml, "null"),
-            1.0
+            similarity::semantic_or_textual(&g.target_yaml, "null"),
+            1.0,
+            "`null` should be accepted as the minimum YAML"
         );
+    }
 
-        // Level 2: deterministic per seed, non-empty mapping.
-        let g2 = registry[1].generate(42);
-        let v2: serde_yaml::Value = serde_yaml::from_str(&g2.target_yaml).unwrap();
-        let m = v2.as_mapping().expect("level 2 produces a mapping");
-        assert!(!m.is_empty());
-        let g2_again = registry[1].generate(42);
-        assert_eq!(
-            g2.target_yaml, g2_again.target_yaml,
-            "same seed should produce the same target"
-        );
-
-        // Level 3: deterministic per seed; produces a mapping of mappings,
-        // each inner mapping has a `type` key.
-        let g3 = registry[2].generate(123);
-        let v3: serde_yaml::Value = serde_yaml::from_str(&g3.target_yaml).unwrap();
-        let m3 = v3.as_mapping().expect("level 3 produces a mapping");
-        assert!(!m3.is_empty());
-        for (_dir, feature) in m3 {
-            let inner = feature.as_mapping().expect("level 3 inner is a mapping");
+    #[test]
+    fn level_02_key_value_is_a_non_empty_mapping() {
+        let g = checked_level(1, 42);
+        let v = parse(&g.target_yaml);
         assert!(
-                inner.get(serde_yaml::Value::String("type".into())).is_some(),
+            !v.as_mapping()
+                .expect("level 2 produces a mapping")
+                .is_empty(),
+            "level 2 yields a non-empty mapping"
+        );
+    }
+
+    #[test]
+    fn level_03_dict_nests_typed_mappings() {
+        // A mapping of mappings; each inner mapping carries a `type` key.
+        let g = checked_level(2, 123);
+        let v = parse(&g.target_yaml);
+        let m = v.as_mapping().expect("level 3 produces a mapping");
+        assert!(!m.is_empty(), "at least one direction");
+        for (_dir, feature) in m {
+            feature.as_mapping().expect("level 3 inner is a mapping");
+            assert!(
+                feature.get("type").is_some(),
                 "each direction must carry a `type` key"
             );
         }
-        let g3_again = registry[2].generate(123);
-        assert_eq!(g3.target_yaml, g3_again.target_yaml);
+    }
+
+    #[test]
+    fn level_04_chest_is_a_list() {
+        // `chest:` is a list of 3–5 item strings.
+        let v = parse(&checked_level(3, 4).target_yaml);
+        let chest = field(&v, "chest").as_sequence().expect("chest is a list");
+        assert!((3..=5).contains(&chest.len()), "chest holds 3–5 items");
+        assert!(chest.iter().all(Value::is_string), "every item is a string");
+    }
+
+    #[test]
+    fn level_05_chambers_is_a_dict_of_lists() {
+        // `chambers:` is a dict of 2–3 lists, 2–3 items each.
+        let v = parse(&checked_level(4, 5).target_yaml);
+        let chambers = field(&v, "chambers")
+            .as_mapping()
+            .expect("chambers is a dict");
+        assert!((2..=3).contains(&chambers.len()), "2–3 chambers");
+        for (_name, items) in chambers {
+            let items = items.as_sequence().expect("each chamber holds a list");
+            assert!((2..=3).contains(&items.len()), "2–3 items per chamber");
+        }
+    }
+
+    #[test]
+    fn level_06_trap_repeats_in_every_room() {
+        // `trap:` is defined once; every room repeats it verbatim, so a
+        // player using `&anchor`/`*alias` parses to the same Value.
+        let v = parse(&checked_level(5, 6).target_yaml);
+        let trap = field(&v, "trap");
+        for key in ["type", "depth", "spikes"] {
+            assert!(trap.get(key).is_some(), "trap carries `{key}`");
+        }
+        let rooms = field(&v, "rooms").as_mapping().expect("rooms is a dict");
+        assert!(!rooms.is_empty(), "at least one room");
+        for (_room, payload) in rooms {
+            assert_eq!(payload, trap, "every room repeats the trap definition");
+        }
+    }
+
+    #[test]
+    fn level_07_floor_map_nests_maps_and_lists() {
+        // `floor:` int + `rooms:` dict; each room nests two lists.
+        let v = parse(&checked_level(6, 7).target_yaml);
+        assert!(field(&v, "floor").is_i64(), "floor is an integer");
+        let rooms = field(&v, "rooms").as_mapping().expect("rooms is a dict");
+        assert!(!rooms.is_empty(), "at least one room");
+        for (_name, room) in rooms {
+            assert!(field(room, "type").is_string(), "room.type is a string");
+            assert!(field(room, "locked").is_bool(), "room.locked is a bool");
+            assert!(field(room, "exits").is_sequence(), "room.exits is a list");
+            assert!(
+                field(room, "contents").is_sequence(),
+                "room.contents is a list"
+            );
+        }
+    }
+
+    #[test]
+    fn level_08_scroll_keeps_explicit_types() {
+        // Explicit types: a multi-line string, a float, and a digit-only
+        // string that must NOT collapse to an integer.
+        let v = parse(&checked_level(7, 8).target_yaml);
+        let scroll = field(&v, "scroll").as_str().expect("scroll is a string");
+        assert!(scroll.contains('\n'), "scroll preserves its newlines");
+        assert!(field(&v, "weight").is_f64(), "weight is a float");
+        let title = field(&v, "title");
+        assert!(title.is_string(), "title stays a string, not an int");
+        assert!(
+            title.as_str().unwrap().chars().all(|c| c.is_ascii_digit()),
+            "title is digit-only — the point of the `!!str` lesson"
+        );
+    }
+
+    #[test]
+    fn level_09_doors_merge_shared_defaults() {
+        // Merge keys: each door carries a literal `<<` whose value is the
+        // shared defaults dict, plus its own override.
+        let v = parse(&checked_level(8, 9).target_yaml);
+        let defaults = field(&v, "door_defaults");
+        for door in ["north_door", "south_door"] {
+            assert_eq!(
+                field(field(&v, door), "<<"),
+                defaults,
+                "{door} merges the shared defaults via `<<`"
+            );
+        }
+        assert!(field(field(&v, "north_door"), "locked").is_bool());
+        assert!(field(field(&v, "south_door"), "material").is_string());
+    }
+
+    #[test]
+    fn level_10_ledger_forgives_numeric_forms() {
+        // The ledger: int gold/silver, float experience, ISO date. The
+        // lesson is numeric forgiveness, so hex must score a perfect match.
+        let g = checked_level(9, 10);
+        let v = parse(&g.target_yaml);
+        let vault = field(&v, "vault");
+        let gold = field(vault, "gold").as_i64().expect("gold is an integer");
+        assert!(field(vault, "silver").is_i64(), "silver is an integer");
+        assert!(field(vault, "experience").is_f64(), "experience is a float");
+        assert!(field(vault, "date").is_string(), "date is an ISO string");
+        let hex_candidate = g
+            .target_yaml
+            .replace(&format!("gold: {gold}"), &format!("gold: 0x{gold:X}"));
+        assert_ne!(hex_candidate, g.target_yaml, "hex rewrite must apply");
+        assert_eq!(
+            similarity::semantic_or_textual(&g.target_yaml, &hex_candidate),
+            1.0,
+            "writing gold in hex must still score a perfect match"
+        );
+    }
+
+    #[test]
+    fn level_11_copies_alias_defined_shapes() {
+        // `shapes:` defines polygons; `copies:` reuses them, so each copy
+        // is structurally identical to one of the definitions.
+        let v = parse(&checked_level(10, 11).target_yaml);
+        let shapes = field(&v, "shapes").as_sequence().expect("shapes is a list");
+        assert!((2..=3).contains(&shapes.len()), "2–3 defined shapes");
+        for s in shapes {
+            assert!(field(s, "name").is_string(), "shape.name is a string");
+            let sides = field(s, "sides").as_i64().expect("shape.sides is an int");
+            assert_eq!(
+                field(s, "interior").as_i64().expect("shape.interior is an int"),
+                (sides - 2) * 180,
+                "interior angle sum follows (n-2)·180"
+            );
+        }
+        let copies = field(&v, "copies").as_sequence().expect("copies is a list");
+        assert!((3..=4).contains(&copies.len()), "3–4 copies");
+        for c in copies {
+            assert!(shapes.contains(c), "every copy aliases a defined shape");
+        }
     }
 }