First levels v0.1.0

src/bin/go.rs

@@ -1,3 +1,21 @@
-fn main() -> anyhow::Result<()> {
-    yamlabyrinth::tui::run()
+use anyhow::Result;
+use clap::Parser;
+
+#[derive(Parser)]
+#[command(name = "go", about = "Traverse the YAML labyrinth")]
+struct Cli {
+    /// Wipe progress and exit.
+    #[arg(long)]
+    reset: bool,
+}
+
+fn main() -> Result<()> {
+    let cli = Cli::parse();
+    if cli.reset {
+        let _ = std::fs::remove_file(yamlabyrinth::progress::save_path());
+        println!("Progress wiped.");
+        return Ok(());
+    }
+    let mut prog = yamlabyrinth::progress::load()?;
+    yamlabyrinth::tui::run(&mut prog)
 }

src/describe.rs

@@ -0,0 +1,38 @@
+//! Per-level natural-language descriptions, rendered with `tera`.
+//!
+//! Each level registers its own template string at startup; the `Describer`
+//! is the registry. The template string lives next to the level's
+//! generator, not in this module.
+
+use tera::{Context, Tera};
+
+pub struct Describer {
+    tera: Tera,
+}
+
+impl Describer {
+    pub fn new() -> Self {
+        Self {
+            tera: Tera::default(),
+        }
+    }
+
+    pub fn register(&mut self, name: &str, template: &str) -> tera::Result<()> {
+        self.tera.add_raw_template(name, template)
+    }
+
+    pub fn render<C: serde::Serialize>(
+        &self,
+        name: &str,
+        ctx: &C,
+    ) -> tera::Result<String> {
+        let ctx = Context::from_serialize(ctx)?;
+        self.tera.render(name, &ctx)
+    }
+}
+
+impl Default for Describer {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/levels/l01_minimum.rs

@@ -0,0 +1,35 @@
+//! Level 1 — the dungeon door. Write the smallest valid YAML.
+//!
+//! Paired design note: `l01.md`.
+
+use serde_yaml::Value;
+
+use super::{Generated, Level};
+
+pub struct Minimum;
+
+impl Level for Minimum {
+    fn id(&self) -> u8 {
+        1
+    }
+
+    fn name(&self) -> &'static str {
+        "The Dungeon Door"
+    }
+
+    fn generate(&self, _seed: u64) -> Generated {
+        // Canonical target: the null document. `---`, `~`, and `null` all
+        // parse to `Value::Null`, so any of them passes via the semantic
+        // short-circuit.
+        let target_yaml = serde_yaml::to_string(&Value::Null).expect("serialise null");
+        Generated {
+            target_yaml,
+            description:
+                "Write the smallest possible valid YAML — a single empty document is enough."
+                    .to_string(),
+            flavor:
+                "A heavy door bars the way. A glyph above it asks only for the smallest valid offering."
+                    .to_string(),
+        }
+    }
+}

src/levels/l02_kv.rs

@@ -0,0 +1,81 @@
+//! Level 2 — key-value pairs. Map each direction to what lies that way.
+//!
+//! Paired design note: `l02.md`.
+
+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 KeyValue;
+
+const DIRECTIONS: &[&str] = &["left", "right", "straight", "back", "up", "down"];
+const FEATURES: &[&str] = &["door", "tunnel", "wall", "stairs", "pit", "altar"];
+
+#[derive(Serialize)]
+struct DescCtx {
+    pairs: Vec<DescPair>,
+}
+
+#[derive(Serialize)]
+struct DescPair {
+    direction: String,
+    feature: String,
+}
+
+impl Level for KeyValue {
+    fn id(&self) -> u8 {
+        2
+    }
+
+    fn name(&self) -> &'static str {
+        "Key-Value Pairs"
+    }
+
+    fn generate(&self, seed: u64) -> Generated {
+        // Seed XOR'd with a per-level constant so the same `current_seed`
+        // produces different content per level.
+        let mut rng = ChaCha8Rng::seed_from_u64(seed ^ 0x0000_0000_0000_0002);
+        let n = rng.gen_range(2..=4);
+        let directions: Vec<&'static str> =
+            DIRECTIONS.choose_multiple(&mut rng, n).copied().collect();
+
+        let mut mapping = Mapping::new();
+        let mut pairs = Vec::with_capacity(directions.len());
+        for d in &directions {
+            let f = *FEATURES.choose(&mut rng).expect("non-empty pool");
+            mapping.insert(
+                Value::String((*d).to_string()),
+                Value::String(f.to_string()),
+            );
+            pairs.push(DescPair {
+                direction: (*d).to_string(),
+                feature: f.to_string(),
+            });
+        }
+
+        let target_yaml =
+            serde_yaml::to_string(&Value::Mapping(mapping)).expect("serialise mapping");
+
+        let mut d = Describer::new();
+        d.register(
+            "l02",
+            "{% for p in pairs %}- {{ p.direction }} leads to a {{ p.feature }}\n{% endfor %}",
+        )
+        .expect("register template");
+        let description = d
+            .render("l02", &DescCtx { pairs })
+            .expect("render template");
+
+        Generated {
+            target_yaml,
+            description,
+            flavor: "You stand at a junction. Map what you see.".to_string(),
+        }
+    }
+}

src/levels/mod.rs

@@ -0,0 +1,67 @@
+//! Levels — hand-written Rust generators paired with design notes.
+//!
+//! Each level is implemented in `l<XX>_<name>.rs` and is the authoritative
+//! source of truth for what target YAML the player must reproduce and how
+//! the description is rendered.
+//!
+//! The paired `l<XX>.md` file is a **design note only**: it documents the
+//! intended scene and a minimal example of the target YAML. `.md` files
+//! are *not* loaded at runtime — there is no `include_str!` and no
+//! markdown parser. If a `.md` and its paired `.rs` ever disagree, the
+//! `.rs` wins.
+
+pub mod l01_minimum;
+pub mod l02_kv;
+
+use serde::{Deserialize, Serialize};
+
+/// Game-wide difficulty. Chosen once on the TierSelect screen; persisted
+/// in `Progress.tier`. Maps to a fixed passing threshold per level.
+#[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+pub enum Difficulty {
+    Easy,
+    Medium,
+    Hard,
+}
+
+impl Difficulty {
+    pub fn threshold(self) -> f64 {
+        match self {
+            Self::Easy => 0.70,
+            Self::Medium => 0.80,
+            Self::Hard => 0.95,
+        }
+    }
+
+    pub fn label(self) -> &'static str {
+        match self {
+            Self::Easy => "Easy (70%)",
+            Self::Medium => "Medium (80%)",
+            Self::Hard => "Hard (95%)",
+        }
+    }
+}
+
+/// What `Level::generate` returns: the canonical target YAML to grade
+/// against, the player-facing description (already rendered), and the
+/// dungeon flavor line.
+pub struct Generated {
+    pub target_yaml: String,
+    pub description: String,
+    pub flavor: String,
+}
+
+/// One level's generator. Implementations live in `l<XX>_<name>.rs`.
+pub trait Level {
+    fn id(&self) -> u8;
+    fn name(&self) -> &'static str;
+    fn generate(&self, seed: u64) -> Generated;
+}
+
+/// Ordered registry of all levels. `registry()[0]` is level 1.
+pub fn registry() -> Vec<Box<dyn Level>> {
+    vec![
+        Box::new(l01_minimum::Minimum),
+        Box::new(l02_kv::KeyValue),
+    ]
+}

src/lib.rs

@@ -3,3 +3,112 @@ pub mod levels;
 pub mod progress;
 pub mod similarity;
 pub mod tui;
+
+#[cfg(test)]
+mod smoke {
+    //! End-to-end wiring test with one hardcoded level (no `Level` trait yet).
+
+    use super::*;
+    use serde::Serialize;
+    use serde_yaml::{Mapping, Value};
+
+    #[derive(Serialize)]
+    struct JunctionCtx {
+        directions: Vec<Direction>,
+    }
+
+    #[derive(Serialize)]
+    struct Direction {
+        name: &'static str,
+        feature: &'static str,
+    }
+
+    #[test]
+    fn one_level_round_trip() {
+        // (1) Describer renders prose for a fake "junction" level.
+        let mut d = describe::Describer::new();
+        d.register(
+            "junction",
+            "You stand at a junction:\n\
+             {% for x in directions %}- {{ x.name }} leads to a {{ x.feature }}\n{% endfor %}",
+        )
+        .unwrap();
+        let prose = d
+            .render(
+                "junction",
+                &JunctionCtx {
+                    directions: vec![
+                        Direction { name: "left", feature: "door" },
+                        Direction { name: "right", feature: "tunnel" },
+                    ],
+                },
+            )
+            .unwrap();
+        assert!(prose.contains("left leads to a door"));
+        assert!(prose.contains("right leads to a tunnel"));
+
+        // (2) Canonical target via serde_yaml — what a generator will do.
+        // A reordered candidate parses to the same Value, so the semantic
+        // short-circuit must score it 1.0.
+        let mut m = Mapping::new();
+        m.insert(Value::String("left".into()), Value::String("door".into()));
+        m.insert(Value::String("right".into()), Value::String("tunnel".into()));
+        let target = serde_yaml::to_string(&Value::Mapping(m)).unwrap();
+        let candidate = "right: tunnel\nleft: door\n";
+        assert_eq!(
+            similarity::semantic_or_textual(&target, candidate),
+            1.0,
+            "reordered keys should still be a perfect semantic match"
+        );
+
+        // (3) Textually-different, semantically-different → ratio in (0, 1).
+        let near_miss = similarity::similarity_ratio("a: 1\nb: 2\n", "a: 1\nb: 3\n");
+        assert!(near_miss > 0.0 && near_miss < 1.0);
+
+        // (4) Progress round-trips through the same YAML pipeline that disk
+        // save/load will use.
+        let p = progress::Progress {
+            tier: Some(levels::Difficulty::Medium),
+            completed: vec![1, 2],
+            current_level: 3,
+            current_seed: 0xCAFE,
+            attempts: 1,
+        };
+        let s = serde_yaml::to_string(&p).unwrap();
+        let loaded: progress::Progress = serde_yaml::from_str(&s).unwrap();
+        assert_eq!(loaded.tier, p.tier);
+        assert_eq!(loaded.current_level, p.current_level);
+        assert_eq!(loaded.current_seed, p.current_seed);
+    }
+
+    #[test]
+    fn levels_generate_canonical_yaml() {
+        let registry = levels::registry();
+        assert_eq!(registry.len(), 2);
+
+        // 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());
+        assert_eq!(
+            similarity::semantic_or_textual(&g1.target_yaml, "---"),
+            1.0,
+            "`---` should be accepted as the minimum YAML"
+        );
+        assert_eq!(
+            similarity::semantic_or_textual(&g1.target_yaml, "null"),
+            1.0
+        );
+
+        // 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"
+        );
+    }
+}

src/progress.rs

@@ -0,0 +1,38 @@
+//! Player progress saved to `./.gameplay/state.yaml`.
+
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+use crate::levels::Difficulty;
+
+#[derive(Default, Serialize, Deserialize)]
+pub struct Progress {
+    pub tier: Option<Difficulty>,
+    pub completed: Vec<u8>,
+    pub current_level: u8,
+    pub current_seed: u64,
+    pub attempts: u32,
+}
+
+pub fn save_path() -> PathBuf {
+    PathBuf::from(".gameplay/state.yaml")
+}
+
+pub fn load() -> Result<Progress> {
+    let path = save_path();
+    if !path.exists() {
+        return Ok(Progress::default());
+    }
+    Ok(serde_yaml::from_str(&std::fs::read_to_string(&path)?)?)
+}
+
+pub fn save(progress: &Progress) -> Result<()> {
+    let path = save_path();
+    // First-run safeguard: `.gameplay/` won't exist yet.
+    if let Some(dir) = path.parent() {
+        std::fs::create_dir_all(dir)?;
+    }
+    std::fs::write(&path, serde_yaml::to_string(progress)?)?;
+    Ok(())
+}

src/similarity.rs

@@ -0,0 +1,29 @@
+//! Line-based YAML similarity with a semantic short-circuit.
+//!
+//! The canonical serialised form is whatever `serde_yaml::to_string` of the
+//! target `Value` produces. Level generators must build the target via
+//! `serde_yaml::to_string` so the player can submit any semantically-equal
+//! YAML and still earn a perfect score.
+
+use similar::TextDiff;
+
+/// Line-based similarity ratio in `[0.0, 1.0]`.
+pub fn similarity_ratio(target: &str, candidate: &str) -> f64 {
+    TextDiff::from_lines(target, candidate).ratio() as f64
+}
+
+/// Primary entry point. If both sides parse to equal `serde_yaml::Value`s,
+/// return `1.0`; otherwise fall back to line-based textual similarity. The
+/// short-circuit is what makes `yes` / `true` and other YAML aliases
+/// forgivable without having to canonicalise the player's submission.
+pub fn semantic_or_textual(target: &str, candidate: &str) -> f64 {
+    if let (Ok(t), Ok(c)) = (
+        serde_yaml::from_str::<serde_yaml::Value>(target),
+        serde_yaml::from_str::<serde_yaml::Value>(candidate),
+    ) {
+        if t == c {
+            return 1.0;
+        }
+    }
+    similarity_ratio(target, candidate)
+}

src/tui.rs

@@ -5,14 +5,40 @@ use crossterm::terminal::{
     disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen,
 };
 use ratatui::backend::CrosstermBackend;
-use ratatui::widgets::{Block, Borders, Paragraph};
-use ratatui::Terminal;
+use ratatui::layout::Rect;
+use ratatui::widgets::{Block, Borders, Paragraph, Wrap};
+use ratatui::{Frame, Terminal};
 use std::io::{stdout, Stdout};
 
-pub fn run() -> Result<()> {
+use crate::levels::{self, Difficulty, Level};
+use crate::progress::{self, Progress};
+use crate::similarity;
+
+enum Screen {
+    Welcome,
+    TierSelect {
+        cursor: u8,
+    },
+    Level,
+    Submit {
+        buf: String,
+    },
+    Result {
+        score: f64,
+        passed: bool,
+        level_name: String,
+    },
+    InvalidYaml {
+        error: String,
+    },
+    ResetConfirm,
+    Completed,
+}
+
+pub fn run(prog: &mut Progress) -> Result<()> {
     install_panic_hook();
     let mut terminal = enter()?;
-    let result = main_loop(&mut terminal);
+    let result = main_loop(&mut terminal, prog);
     leave()?;
     result
 }
@@ -37,23 +63,309 @@ fn leave() -> Result<()> {
     Ok(())
 }
 
-fn main_loop(terminal: &mut Terminal<CrosstermBackend<Stdout>>) -> Result<()> {
-    loop {
-        terminal.draw(|frame| {
-            let block = Block::default()
-                .borders(Borders::ALL)
-                .title(" YAMLabyrinth ");
-            let body = Paragraph::new(
-                "Welcome to the YAML labyrinth.\n\nPress [q] to flee.",
-            )
-            .block(block);
-            frame.render_widget(body, frame.size());
-        })?;
+fn initial_screen(prog: &Progress, registry_len: usize) -> Screen {
+    match (prog.tier, prog.current_level) {
+        (None, 0) => Screen::Welcome,
+        (None, _) => Screen::TierSelect { cursor: 0 },
+        (Some(_), 0) => Screen::TierSelect { cursor: 0 },
+        (Some(_), n) if (n as usize) > registry_len => Screen::Completed,
+        (Some(_), _) => Screen::Level,
+    }
+}
 
-        if let Event::Key(key) = event::read()? {
-            if key.code == KeyCode::Char('q') {
-                return Ok(());
-            }
+fn main_loop(
+    terminal: &mut Terminal<CrosstermBackend<Stdout>>,
+    prog: &mut Progress,
+) -> Result<()> {
+    let registry = levels::registry();
+    let mut screen = initial_screen(prog, registry.len());
+
+    loop {
+        terminal.draw(|frame| render(frame, &screen, prog, &registry))?;
+        let Event::Key(key) = event::read()? else {
+            continue;
+        };
+
+        // Swap `screen` out so we can match by value, then assign the new
+        // screen back. `Screen::Welcome` is just a placeholder during the
+        // swap; `step` never observes it.
+        let current = std::mem::replace(&mut screen, Screen::Welcome);
+        match step(current, key.code, prog, &registry)? {
+            Transition::To(next) => screen = next,
+            Transition::Quit => return Ok(()),
         }
     }
 }
+
+enum Transition {
+    To(Screen),
+    Quit,
+}
+
+fn step(
+    screen: Screen,
+    key: KeyCode,
+    prog: &mut Progress,
+    registry: &[Box<dyn Level>],
+) -> Result<Transition> {
+    use Transition::*;
+
+    Ok(match (screen, key) {
+        // Welcome ------------------------------------------------------------
+        (Screen::Welcome, KeyCode::Enter) => To(Screen::TierSelect { cursor: 0 }),
+        (Screen::Welcome, KeyCode::Char('q')) => Quit,
+
+        // TierSelect ---------------------------------------------------------
+        (Screen::TierSelect { cursor }, KeyCode::Up) => To(Screen::TierSelect {
+            cursor: cursor.saturating_sub(1),
+        }),
+        (Screen::TierSelect { cursor }, KeyCode::Down) => To(Screen::TierSelect {
+            cursor: (cursor + 1).min(2),
+        }),
+        (Screen::TierSelect { cursor }, KeyCode::Enter) => {
+            let tier = match cursor {
+                0 => Difficulty::Easy,
+                1 => Difficulty::Medium,
+                _ => Difficulty::Hard,
+            };
+            prog.tier = Some(tier);
+            if prog.current_level == 0 {
+                prog.current_level = 1;
+                prog.current_seed = rand::random();
+            }
+            progress::save(prog)?;
+            To(Screen::Level)
+        }
+        (Screen::TierSelect { .. }, KeyCode::Char('q')) => Quit,
+
+        // Level --------------------------------------------------------------
+        (Screen::Level, KeyCode::Char('s')) => To(Screen::Submit { buf: String::new() }),
+        (Screen::Level, KeyCode::Char('r')) => To(Screen::ResetConfirm),
+        (Screen::Level, KeyCode::Char('q')) => Quit,
+
+        // Submit -------------------------------------------------------------
+        (Screen::Submit { mut buf }, KeyCode::Char(c)) => {
+            buf.push(c);
+            To(Screen::Submit { buf })
+        }
+        (Screen::Submit { mut buf }, KeyCode::Backspace) => {
+            buf.pop();
+            To(Screen::Submit { buf })
+        }
+        (Screen::Submit { .. }, KeyCode::Esc) => To(Screen::Level),
+        (Screen::Submit { buf }, KeyCode::Enter) => To(grade(buf.trim(), prog, registry)?),
+
+        // Result -------------------------------------------------------------
+        (Screen::Result { passed: true, .. }, _) => {
+            if (prog.current_level as usize) > registry.len() {
+                To(Screen::Completed)
+            } else {
+                To(Screen::Level)
+            }
+        }
+        (Screen::Result { passed: false, .. }, _) => To(Screen::Level),
+
+        // InvalidYaml --------------------------------------------------------
+        (Screen::InvalidYaml { .. }, _) => To(Screen::Submit { buf: String::new() }),
+
+        // ResetConfirm -------------------------------------------------------
+        (Screen::ResetConfirm, KeyCode::Char('y')) => {
+            let _ = std::fs::remove_file(progress::save_path());
+            *prog = Progress::default();
+            To(Screen::Welcome)
+        }
+        (Screen::ResetConfirm, _) => To(Screen::Level),
+
+        // Completed ----------------------------------------------------------
+        (Screen::Completed, KeyCode::Char('q')) => Quit,
+        (Screen::Completed, KeyCode::Char('r')) => To(Screen::ResetConfirm),
+
+        // Anything else: stay where we are.
+        (other, _) => To(other),
+    })
+}
+
+/// Read the player's file, parse it, score it, advance progress on a pass,
+/// and choose the next screen. Returns `Result` (`InvalidYaml` or `Result`).
+fn grade(path: &str, prog: &mut Progress, registry: &[Box<dyn Level>]) -> Result<Screen> {
+    let candidate = match std::fs::read_to_string(path) {
+        Ok(s) => s,
+        Err(e) => {
+            return Ok(Screen::InvalidYaml {
+                error: format!("could not read file: {e}"),
+            });
+        }
+    };
+
+    // Parse-first guard: invalid YAML is a wrong *format*, not a wrong
+    // *answer* — no scoring, no attempts bump.
+    if let Err(e) = serde_yaml::from_str::<serde_yaml::Value>(&candidate) {
+        return Ok(Screen::InvalidYaml { error: e.to_string() });
+    }
+
+    let idx = (prog.current_level - 1) as usize;
+    let level = &registry[idx];
+    let g = level.generate(prog.current_seed);
+    let score = similarity::semantic_or_textual(&g.target_yaml, &candidate);
+    let threshold = prog
+        .tier
+        .expect("tier set before reaching the Level screen")
+        .threshold();
+    let passed = score >= threshold;
+    let level_name = level.name().to_string();
+    let level_id = level.id();
+
+    if passed {
+        prog.completed.push(level_id);
+        prog.current_level += 1;
+        prog.current_seed = rand::random();
+    } else {
+        prog.attempts += 1;
+    }
+    progress::save(prog)?;
+
+    Ok(Screen::Result {
+        score,
+        passed,
+        level_name,
+    })
+}
+
+// -- rendering --------------------------------------------------------------
+
+fn render(
+    frame: &mut Frame,
+    screen: &Screen,
+    prog: &Progress,
+    registry: &[Box<dyn Level>],
+) {
+    let area = frame.size();
+    match screen {
+        Screen::Welcome => render_welcome(frame, area),
+        Screen::TierSelect { cursor } => render_tier_select(frame, area, *cursor),
+        Screen::Level => render_level(frame, area, prog, registry),
+        Screen::Submit { buf } => render_submit(frame, area, buf),
+        Screen::Result {
+            score,
+            passed,
+            level_name,
+        } => render_result(frame, area, *score, *passed, level_name, prog),
+        Screen::InvalidYaml { error } => render_invalid_yaml(frame, area, error),
+        Screen::ResetConfirm => render_reset_confirm(frame, area),
+        Screen::Completed => render_completed(frame, area),
+    }
+}
+
+fn screen_widget<'a>(title: String, body: String) -> Paragraph<'a> {
+    Paragraph::new(body)
+        .block(Block::default().borders(Borders::ALL).title(title))
+        .wrap(Wrap { trim: false })
+}
+
+fn render_welcome(frame: &mut Frame, area: Rect) {
+    let body = "\n\
+        You stand at the entrance to the YAML labyrinth.\n\
+        Within, broken syntax festers and dictionaries\n\
+        sprawl like vines. Reach the heart of it.\n\
+        \n\
+        [Enter] begin · [q] flee"
+        .to_string();
+    frame.render_widget(screen_widget(" YAMLabyrinth ".to_string(), body), area);
+}
+
+fn render_tier_select(frame: &mut Frame, area: Rect, cursor: u8) {
+    let rows = [
+        ("Easy", "70 %", "forgive small slips"),
+        ("Medium", "80 %", "most details must match"),
+        ("Hard", "95 %", "only near-perfect passes"),
+    ];
+    let mut body = String::from("\n");
+    for (i, (name, pct, hint)) in rows.iter().enumerate() {
+        let marker = if i == cursor as usize { ">" } else { " " };
+        body.push_str(&format!("  {marker} {name:<7} ({pct})   {hint}\n"));
+    }
+    body.push_str("\n↑/↓ choose · [Enter] confirm · [q] quit");
+    frame.render_widget(screen_widget(" Choose your tier ".to_string(), body), area);
+}
+
+fn render_level(
+    frame: &mut Frame,
+    area: Rect,
+    prog: &Progress,
+    registry: &[Box<dyn Level>],
+) {
+    let idx = (prog.current_level - 1) as usize;
+    let level = &registry[idx];
+    let g = level.generate(prog.current_seed);
+    let tier_label = prog.tier.map(|t| t.label()).unwrap_or("?");
+    let title = format!(
+        " Level {}: {} · Tier: {} ",
+        level.id(),
+        level.name(),
+        tier_label
+    );
+    let body = format!(
+        "\n{}\n\n{}\nWrite your YAML answer in a file, then\n[s] submit · [r] reset · [q] flee",
+        g.flavor, g.description
+    );
+    frame.render_widget(screen_widget(title, body), area);
+}
+
+fn render_submit(frame: &mut Frame, area: Rect, buf: &str) {
+    let body = format!(
+        "\nPath to your answer YAML:\n\n> {buf}_\n\n[Enter] grade · [Esc] cancel"
+    );
+    frame.render_widget(screen_widget(" Submit your answer ".to_string(), body), area);
+}
+
+fn render_result(
+    frame: &mut Frame,
+    area: Rect,
+    score: f64,
+    passed: bool,
+    level_name: &str,
+    prog: &Progress,
+) {
+    let threshold = prog
+        .tier
+        .map(|t| t.threshold())
+        .unwrap_or(0.0);
+    let (title, narration) = if passed {
+        (
+            format!(" {level_name} cleared "),
+            "The door creaks open. You step deeper into the labyrinth.",
+        )
+    } else {
+        (
+            " Not yet ".to_string(),
+            "The labyrinth resists. Refine your YAML and try again.",
+        )
+    };
+    let body = format!(
+        "\nScore {:.0} %   Threshold {:.0} %\n\n{}\n\n[Enter] continue",
+        score * 100.0,
+        threshold * 100.0,
+        narration,
+    );
+    frame.render_widget(screen_widget(title, body), area);
+}
+
+fn render_invalid_yaml(frame: &mut Frame, area: Rect, error: &str) {
+    let body = format!(
+        "\n{error}\n\nFix the syntax and try again.\n\n[Enter] back to submit"
+    );
+    frame.render_widget(
+        screen_widget(" Couldn't parse your YAML ".to_string(), body),
+        area,
+    );
+}
+
+fn render_reset_confirm(frame: &mut Frame, area: Rect) {
+    let body = "\nWipe progress and start over?\n\n[y] yes, wipe · any other key cancels".to_string();
+    frame.render_widget(screen_widget(" Reset? ".to_string(), body), area);
+}
+
+fn render_completed(frame: &mut Frame, area: Rect) {
+    let body = "\nYou cleared the YAML labyrinth.\n\n[r] reset and replay · [q] quit".to_string();
+    frame.render_widget(screen_widget(" Labyrinth complete ".to_string(), body), area);
+}