diff --git a/crates/city/src/app.rs b/crates/city/src/app.rs
index 991d442..7a92fd5 100644
--- a/crates/city/src/app.rs
+++ b/crates/city/src/app.rs
@@ -19,6 +19,7 @@ pub const FRAME: Duration = Duration::from_micros(33_333);
 pub struct AppState {
     pub params: GenParams,
     pub city: Option<City>,
+    pub player: Option<crate::walker::Player>,
     pub style: StylePack,
     pub tick: u64,
     status: Option<(String, u64)>,
@@ -35,6 +36,7 @@ impl AppState {
         AppState {
             params: GenParams::default(),
             city: None,
+            player: None,
             style: StylePack::load().expect("embedded style pack is valid"),
             tick: 0,
             status: None,
diff --git a/crates/city/src/main.rs b/crates/city/src/main.rs
index e5deff5..de7b459 100644
--- a/crates/city/src/main.rs
+++ b/crates/city/src/main.rs
@@ -11,6 +11,7 @@ mod save;
 mod screens;
 mod term;
 mod ui;
+mod walker;
 
 fn main() -> anyhow::Result<()> {
     cli::run()
diff --git a/crates/city/src/screens/configure.rs b/crates/city/src/screens/configure.rs
new file mode 100644
index 0000000..7150445
--- /dev/null
+++ b/crates/city/src/screens/configure.rs
@@ -0,0 +1,27 @@
+//! The configure screen: a form over `GenParams` with a live preview card.
+
+use crate::app::{AppState, Screen, ScreenCmd};
+use citygen::GenParams;
+use crossterm::event::KeyEvent;
+use ratatui::Frame;
+
+pub struct Configure {
+    params: GenParams,
+    opened: u64,
+}
+
+impl Configure {
+    pub fn new(params: GenParams, tick: u64) -> Self {
+        Configure {
+            params,
+            opened: tick,
+        }
+    }
+}
+
+impl Screen for Configure {
+    fn update(&mut self, _st: &mut AppState, _keys: &[KeyEvent]) -> ScreenCmd {
+        ScreenCmd::Stay
+    }
+    fn draw(&self, _st: &AppState, _f: &mut Frame) {}
+}
diff --git a/crates/city/src/screens/generating.rs b/crates/city/src/screens/generating.rs
new file mode 100644
index 0000000..bffe112
--- /dev/null
+++ b/crates/city/src/screens/generating.rs
@@ -0,0 +1,367 @@
+//! The generation screen: the city grows in the viewport while a stage checklist fills.
+
+use crate::app::{AppState, Screen, ScreenCmd, TransitionKind};
+use crate::render::viewport::{Camera, MapView};
+use crate::render::weather::Weather;
+use crate::ui::panel::boxed;
+use citygen::rng::hash64;
+use citygen::{GenParams, Generator, Pos, Progress, Stage, StratumKind};
+use crossterm::event::{KeyCode, KeyEvent};
+use ratatui::Frame;
+use ratatui::layout::{Constraint, Direction, Layout, Rect};
+use ratatui::style::{Color, Modifier, Style};
+use ratatui::text::{Line, Span};
+use ratatui::widgets::{Paragraph, Widget};
+
+const PANEL_W: u16 = 36;
+const BAR_W: usize = 16;
+
+pub struct Generating {
+    generator: Option<Generator>,
+    params: GenParams,
+    pub steps_per_frame: u32,
+    pub paused: bool,
+    current: Option<(Stage, f32)>,
+    done: Vec<Stage>,
+    cam: Camera,
+    error: Option<String>,
+    started: u64,
+}
+
+/// Short stage names for the checklist.
+fn short(stage: Stage) -> &'static str {
+    match stage {
+        Stage::Terrain => "Terrain",
+        Stage::Districts => "Districts",
+        Stage::Arterials => "Arterials",
+        Stage::Streets => "Streets",
+        Stage::Lots => "Buildings",
+        Stage::Verticals => "Strata",
+        Stage::Interiors => "Interiors",
+        Stage::Connectivity => "Links",
+        Stage::Dressing => "Neon",
+        Stage::Naming => "Names",
+        Stage::Net => "Net",
+    }
+}
+
+impl Generating {
+    pub fn new(params: GenParams, tick: u64) -> anyhow::Result<Self> {
+        let generator = Generator::new(params.clone())?;
+        let mut cam = Camera::default();
+        cam.snap(generator.city().size.center());
+        Ok(Generating {
+            generator: Some(generator),
+            params,
+            steps_per_frame: 8,
+            paused: false,
+            current: None,
+            done: Vec::new(),
+            cam,
+            error: None,
+            started: tick,
+        })
+    }
+
+    /// Something that changes whenever generation advances; used by tests.
+    pub fn progress_marker(&self) -> (usize, Option<(Stage, u32)>) {
+        (
+            self.done.len(),
+            self.current.map(|(s, p)| (s, (p * 1000.0) as u32)),
+        )
+    }
+
+    fn step_once(&mut self) -> bool {
+        let Some(generator) = self.generator.as_mut() else {
+            return false;
+        };
+        match generator.step() {
+            Progress::Running { stage, pct } => {
+                if let Some((prev, _)) = self.current
+                    && prev != stage
+                    && !self.done.contains(&prev)
+                {
+                    self.done.push(prev);
+                }
+                self.current = Some((stage, pct));
+                true
+            }
+            Progress::Done => {
+                if let Some((prev, _)) = self.current
+                    && !self.done.contains(&prev)
+                {
+                    self.done.push(prev);
+                }
+                false
+            }
+        }
+    }
+
+    fn finish(&mut self, st: &mut AppState) -> ScreenCmd {
+        let Some(generator) = self.generator.take() else {
+            return ScreenCmd::Stay;
+        };
+        match generator.finish() {
+            Ok(city) => {
+                st.params = self.params.clone();
+                st.city = Some(city);
+                st.player = None;
+                ScreenCmd::Switch {
+                    to: crate::screens::explore_screen(st.tick),
+                    fx: TransitionKind::Glitch,
+                }
+            }
+            Err(e) => {
+                self.error = Some(e.to_string());
+                ScreenCmd::Stay
+            }
+        }
+    }
+}
+
+impl Screen for Generating {
+    fn update(&mut self, st: &mut AppState, keys: &[KeyEvent]) -> ScreenCmd {
+        let mut skip = false;
+        for k in keys {
+            match k.code {
+                KeyCode::Char(' ') => self.paused = !self.paused,
+                KeyCode::Char('+') | KeyCode::Char('=') => {
+                    self.steps_per_frame = (self.steps_per_frame * 2).min(64)
+                }
+                KeyCode::Char('-') => self.steps_per_frame = (self.steps_per_frame / 2).max(1),
+                KeyCode::Enter => skip = true,
+                KeyCode::Char('r') => {
+                    let seed = hash64(self.params.seed, st.tick);
+                    match Generating::new(self.params.clone().with_seed(seed), st.tick) {
+                        Ok(next) => {
+                            return ScreenCmd::Switch {
+                                to: Box::new(next),
+                                fx: TransitionKind::Glitch,
+                            };
+                        }
+                        Err(e) => st.set_status(e.to_string(), 90),
+                    }
+                }
+                KeyCode::Esc => {
+                    return ScreenCmd::Switch {
+                        to: Box::new(crate::screens::configure::Configure::new(
+                            self.params.clone(),
+                            st.tick,
+                        )),
+                        fx: TransitionKind::SlideUp,
+                    };
+                }
+                _ => {}
+            }
+        }
+        if self.error.is_some() || self.generator.is_none() {
+            return ScreenCmd::Stay;
+        }
+        let mut running = true;
+        if skip {
+            while running {
+                running = self.step_once();
+            }
+        } else if !self.paused {
+            for _ in 0..self.steps_per_frame {
+                running = self.step_once();
+                if !running {
+                    break;
+                }
+            }
+        }
+        if !running {
+            return self.finish(st);
+        }
+        ScreenCmd::Stay
+    }
+
+    fn draw(&self, st: &AppState, f: &mut Frame) {
+        let area = f.area();
+        let cols = Layout::default()
+            .direction(Direction::Horizontal)
+            .constraints([Constraint::Min(10), Constraint::Length(PANEL_W)])
+            .split(area);
+        let map_area = cols[0];
+        let panel = cols[1];
+
+        if let Some(generator) = &self.generator {
+            let city = generator.city();
+            let mut cam = self.cam;
+            let drift = ((st.tick as f32) / 90.0).sin() * city.size.w as f32 / 6.0;
+            cam.target(Pos::new(
+                city.size.center().x + drift as i32,
+                city.size.center().y,
+            ));
+            cam.clamp(city.size, map_area.width, map_area.height);
+            cam.x += (cam.tx as f32 - cam.x) * 0.1;
+            cam.y += (cam.ty as f32 - cam.y) * 0.1;
+            MapView {
+                city,
+                stratum: StratumKind::Street,
+                origin: cam.origin(map_area.width, map_area.height),
+                tick: st.tick,
+                style: &st.style,
+                vis: None,
+                overlays: &[&Weather],
+                cursor: None,
+            }
+            .render(map_area, f.buffer_mut());
+        }
+
+        let title = format!("GENERATING  seed {}", self.params.seed);
+        let block = boxed(&title);
+        let inner = block.inner(panel);
+        f.render_widget(block, panel);
+        let mut lines: Vec<Line> = Vec::new();
+        lines.push(Line::from(Span::styled(
+            format!(
+                " {}x{}  {} districts",
+                self.params.size.size().w,
+                self.params.size.size().h,
+                self.params.districts
+            ),
+            Style::default().fg(Color::Rgb(120, 130, 145)),
+        )));
+        lines.push(Line::from(""));
+        for stage in Stage::ALL {
+            let done = self.done.contains(&stage);
+            let active = self.current.map(|(s, _)| s) == Some(stage) && !done;
+            let line = if done {
+                Line::from(Span::styled(
+                    format!(" [✓] {:<10}", short(stage)),
+                    Style::default().fg(Color::Rgb(90, 160, 120)),
+                ))
+            } else if active {
+                let pct = self.current.map(|(_, p)| p).unwrap_or(0.0);
+                let filled = (pct * BAR_W as f32).round() as usize;
+                let bar: String = (0..BAR_W)
+                    .map(|i| if i < filled { '▓' } else { '░' })
+                    .collect();
+                Line::from(vec![
+                    Span::styled(
+                        format!(" [▸] {:<10} ", short(stage)),
+                        Style::default()
+                            .fg(Color::Rgb(0, 229, 255))
+                            .add_modifier(Modifier::BOLD),
+                    ),
+                    Span::styled(bar, Style::default().fg(Color::Rgb(0, 200, 230))),
+                    Span::styled(
+                        format!(" {:>3.0}%", pct * 100.0),
+                        Style::default().fg(Color::Rgb(180, 190, 200)),
+                    ),
+                ])
+            } else {
+                Line::from(Span::styled(
+                    format!(" [ ] {:<10}", short(stage)),
+                    Style::default().fg(Color::Rgb(80, 88, 100)),
+                ))
+            };
+            lines.push(line);
+        }
+        lines.push(Line::from(""));
+        if let Some((stage, _)) = self.current {
+            lines.push(Line::from(Span::styled(
+                format!(" {}…", stage.label()),
+                Style::default().fg(Color::Rgb(160, 170, 185)),
+            )));
+        }
+        if let Some(e) = &self.error {
+            lines.push(Line::from(""));
+            lines.push(Line::from(Span::styled(
+                format!(" {e}"),
+                Style::default().fg(Color::Rgb(255, 80, 100)),
+            )));
+            lines.push(Line::from(Span::styled(
+                " r reseed · esc back",
+                Style::default().fg(Color::Rgb(120, 130, 145)),
+            )));
+        } else {
+            let state = if self.paused { "paused" } else { "running" };
+            lines.push(Line::from(Span::styled(
+                format!(" {state} · x{} per frame", self.steps_per_frame),
+                Style::default().fg(Color::Rgb(120, 130, 145)),
+            )));
+        }
+        let hint_y = inner.bottom().saturating_sub(1);
+        f.render_widget(Paragraph::new(lines), inner);
+        if hint_y > inner.y {
+            f.render_widget(
+                Paragraph::new(Span::styled(
+                    " space pause · +/- speed · enter skip",
+                    Style::default().fg(Color::Rgb(100, 110, 125)),
+                )),
+                Rect::new(inner.x, hint_y, inner.width, 1),
+            );
+        }
+        let _ = self.started;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::app::{AppState, Screen, ScreenCmd};
+    use crate::screens::testutil::{buffer_text, key};
+    use citygen::{GenParams, SizePreset};
+    use crossterm::event::KeyCode;
+    use ratatui::Terminal;
+    use ratatui::backend::TestBackend;
+
+    fn params() -> GenParams {
+        GenParams {
+            seed: 2,
+            size: SizePreset::Custom { w: 80, h: 40 },
+            districts: 4,
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn generating_reaches_explore() {
+        let mut st = AppState::new();
+        let mut g = Generating::new(params(), 0).unwrap();
+        let mut t = Terminal::new(TestBackend::new(100, 30)).unwrap();
+        t.draw(|f| g.draw(&st, f)).unwrap();
+        let text = buffer_text(t.backend().buffer());
+        assert!(text.contains("Terrain") && text.contains("Net"), "{text}");
+        let mut cmd = ScreenCmd::Stay;
+        for _ in 0..100_000 {
+            st.tick += 1;
+            cmd = g.update(&mut st, &[key(KeyCode::Enter)]);
+            if !matches!(cmd, ScreenCmd::Stay) {
+                break;
+            }
+        }
+        assert!(matches!(cmd, ScreenCmd::Switch { .. }));
+        assert!(st.city.is_some());
+        assert_eq!(st.params.seed, 2);
+    }
+
+    #[test]
+    fn generating_pauses_and_changes_speed() {
+        let mut st = AppState::new();
+        let mut g = Generating::new(params(), 0).unwrap();
+        g.update(&mut st, &[key(KeyCode::Char(' '))]);
+        assert!(g.paused);
+        let before = g.progress_marker();
+        for _ in 0..5 {
+            st.tick += 1;
+            g.update(&mut st, &[]);
+        }
+        assert_eq!(g.progress_marker(), before);
+        g.update(&mut st, &[key(KeyCode::Char(' '))]);
+        g.update(&mut st, &[key(KeyCode::Char('+'))]);
+        assert_eq!(g.steps_per_frame, 16);
+        for _ in 0..10 {
+            g.update(&mut st, &[key(KeyCode::Char('-'))]);
+        }
+        assert_eq!(g.steps_per_frame, 1);
+        assert!(matches!(
+            g.update(&mut st, &[key(KeyCode::Esc)]),
+            ScreenCmd::Switch { .. }
+        ));
+        let mut t = Terminal::new(TestBackend::new(100, 30)).unwrap();
+        t.draw(|f| g.draw(&st, f)).unwrap();
+    }
+}
diff --git a/crates/city/src/screens/mod.rs b/crates/city/src/screens/mod.rs
index f8f2ca0..d08479f 100644
--- a/crates/city/src/screens/mod.rs
+++ b/crates/city/src/screens/mod.rs
@@ -4,6 +4,9 @@ use crate::app::{AppState, Screen, ScreenCmd};
 use crossterm::event::{KeyCode, KeyEvent};
 use ratatui::Frame;
 
+pub mod configure;
+pub mod generating;
+
 /// Draws nothing; stands in until the title screen lands.
 pub struct Blank;
 
@@ -26,6 +29,11 @@ pub fn initial() -> impl Screen {
     Blank
 }
 
+/// The screen shown once a city exists (explore mode). Wired to the map screen later.
+pub fn explore_screen(_tick: u64) -> Box<dyn Screen> {
+    Box::new(Blank)
+}
+
 #[cfg(test)]
 pub(crate) mod testutil {
     use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
diff --git a/crates/city/src/walker/mod.rs b/crates/city/src/walker/mod.rs
new file mode 100644
index 0000000..ae645e1
--- /dev/null
+++ b/crates/city/src/walker/mod.rs
@@ -0,0 +1,5 @@
+//! The walker: the player's `@`, movement, connectors and field of view.
+
+/// The player. Filled in by the walker task; declared here so app state can hold one.
+#[derive(Clone, Debug)]
+pub struct Player;