basic start and end markers

src/exporter.rs

@@ -6,7 +6,7 @@ use image::{DynamicImage, ImageFormat, RgbaImage, imageops::FilterType};
 use rfd::FileDialog;
 use tiny_skia::{FillRule, Paint, PathBuilder, Pixmap, Rect, Stroke, StrokeDash, Transform};
 
-use crate::layout::{Door, DungeonLayout, Room, Window, WindowSide, corridor_cells};
+use crate::layout::{AreaMarker, Door, DungeonLayout, Room, Window, WindowSide, corridor_cells};
 use crate::ui::{ExportFormat, MaskFormat, UiSettings};
 
 const BG: (u8, u8, u8, u8) = (24, 24, 26, 255);
@@ -20,6 +20,8 @@ const SECRET_DOOR: (u8, u8, u8, u8) = (170, 80, 170, 255);
 const ARCHWAY: (u8, u8, u8, u8) = (230, 140, 60, 255);
 const WINDOW: (u8, u8, u8, u8) = (70, 130, 220, 255);
 const WHITE: (u8, u8, u8, u8) = (255, 255, 255, 255);
+const START_MARKER: (u8, u8, u8, u8) = (60, 220, 200, 255);
+const END_MARKER: (u8, u8, u8, u8) = (240, 90, 90, 255);
 
 pub enum ExportTarget {
     File(PathBuf),
@@ -274,6 +276,13 @@ fn render_pixmap(layout: &DungeonLayout, settings: &UiSettings) -> Result<Pixmap
         draw_window(&mut pixmap, &g, window, door_w, WINDOW, style);
     }
 
+    if let Some(marker) = layout.start_marker.as_ref() {
+        draw_area_marker(&mut pixmap, &g, marker, "S", START_MARKER, settings.colorblind_mode);
+    }
+    if let Some(marker) = layout.end_marker.as_ref() {
+        draw_area_marker(&mut pixmap, &g, marker, "E", END_MARKER, settings.colorblind_mode);
+    }
+
     Ok(pixmap)
 }
 
@@ -668,6 +677,13 @@ fn build_svg(layout: &DungeonLayout, settings: &UiSettings) -> String {
         }
     }
 
+    if let Some(marker) = layout.start_marker.as_ref() {
+        append_svg_area_marker(&mut s, &g, marker, "S", START_MARKER, settings.colorblind_mode);
+    }
+    if let Some(marker) = layout.end_marker.as_ref() {
+        append_svg_area_marker(&mut s, &g, marker, "E", END_MARKER, settings.colorblind_mode);
+    }
+
     s.push_str("</svg>\n");
     s
 }
@@ -746,6 +762,91 @@ fn fill_rect_room(pixmap: &mut Pixmap, g: &ExportGeometry, room: &Room, color: (
     pixmap.fill_rect(rect, &paint, Transform::identity(), None);
 }
 
+fn fill_rect_marker(
+    pixmap: &mut Pixmap,
+    g: &ExportGeometry,
+    marker: &AreaMarker,
+    color: (u8, u8, u8, u8),
+) {
+    let Some(rect) = Rect::from_xywh(
+        g.left() + marker.cell.0 as f32 * g.cell,
+        g.top() + marker.cell.1 as f32 * g.cell,
+        marker.size as f32 * g.cell,
+        marker.size as f32 * g.cell,
+    ) else {
+        return;
+    };
+    let mut paint = Paint::default();
+    paint.set_color_rgba8(color.0, color.1, color.2, color.3);
+    pixmap.fill_rect(rect, &paint, Transform::identity(), None);
+}
+
+fn draw_area_marker(
+    pixmap: &mut Pixmap,
+    g: &ExportGeometry,
+    marker: &AreaMarker,
+    label: &str,
+    color: (u8, u8, u8, u8),
+    colorblind_mode: bool,
+) {
+    let overlay = (color.0, color.1, color.2, if colorblind_mode { 56 } else { 90 });
+    fill_rect_marker(pixmap, g, marker, overlay);
+
+    let x = g.left() + marker.cell.0 as f32 * g.cell;
+    let y = g.top() + marker.cell.1 as f32 * g.cell;
+    let w = marker.size as f32 * g.cell;
+    let h = marker.size as f32 * g.cell;
+    draw_wall_segment(pixmap, x, y, x + w, y, 3.0, color);
+    draw_wall_segment(pixmap, x, y + h, x + w, y + h, 3.0, color);
+    draw_wall_segment(pixmap, x, y, x, y + h, 3.0, color);
+    draw_wall_segment(pixmap, x + w, y, x + w, y + h, 3.0, color);
+
+    let symbol = if colorblind_mode { BLACK } else { WHITE };
+    if label == "S" {
+        draw_line(
+            pixmap,
+            x + w * 0.25,
+            y + h * 0.75,
+            x + w * 0.5,
+            y + h * 0.25,
+            4.0,
+            symbol,
+            DoorStyle::Solid,
+        );
+        draw_line(
+            pixmap,
+            x + w * 0.5,
+            y + h * 0.25,
+            x + w * 0.75,
+            y + h * 0.75,
+            4.0,
+            symbol,
+            DoorStyle::Solid,
+        );
+    } else {
+        draw_line(
+            pixmap,
+            x + w * 0.25,
+            y + h * 0.25,
+            x + w * 0.75,
+            y + h * 0.75,
+            4.0,
+            symbol,
+            DoorStyle::Solid,
+        );
+        draw_line(
+            pixmap,
+            x + w * 0.75,
+            y + h * 0.25,
+            x + w * 0.25,
+            y + h * 0.75,
+            4.0,
+            symbol,
+            DoorStyle::Solid,
+        );
+    }
+}
+
 // Draw a filled circle for dot patterns.
 fn draw_dot(pixmap: &mut Pixmap, cx: f32, cy: f32, radius: f32, color: (u8, u8, u8, u8)) {
     let mut pb = PathBuilder::new();
@@ -1007,6 +1108,56 @@ fn append_svg_walls(
     }
 }
 
+fn append_svg_area_marker(
+    out: &mut String,
+    g: &ExportGeometry,
+    marker: &AreaMarker,
+    label: &str,
+    color: (u8, u8, u8, u8),
+    colorblind_mode: bool,
+) {
+    let x = g.left() + marker.cell.0 as f32 * g.cell;
+    let y = g.top() + marker.cell.1 as f32 * g.cell;
+    let w = marker.size as f32 * g.cell;
+    let h = marker.size as f32 * g.cell;
+    let alpha = if colorblind_mode { 0.22 } else { 0.35 };
+    let _ = writeln!(
+        out,
+        "<rect x='{x}' y='{y}' width='{w}' height='{h}' fill='rgb({},{},{})' fill-opacity='{alpha}' stroke='rgb({},{},{})' stroke-width='3'/>",
+        color.0, color.1, color.2, color.0, color.1, color.2
+    );
+    let symbol = if colorblind_mode { "black" } else { "white" };
+    if label == "S" {
+        let _ = writeln!(
+            out,
+            "<polyline points='{},{} {},{} {},{}' fill='none' stroke='{symbol}' stroke-width='4' stroke-linecap='round' stroke-linejoin='round'/>",
+            x + w * 0.25,
+            y + h * 0.75,
+            x + w * 0.5,
+            y + h * 0.25,
+            x + w * 0.75,
+            y + h * 0.75
+        );
+    } else {
+        let _ = writeln!(
+            out,
+            "<line x1='{}' y1='{}' x2='{}' y2='{}' stroke='{symbol}' stroke-width='4' stroke-linecap='round'/>",
+            x + w * 0.25,
+            y + h * 0.25,
+            x + w * 0.75,
+            y + h * 0.75
+        );
+        let _ = writeln!(
+            out,
+            "<line x1='{}' y1='{}' x2='{}' y2='{}' stroke='{symbol}' stroke-width='4' stroke-linecap='round'/>",
+            x + w * 0.75,
+            y + h * 0.25,
+            x + w * 0.25,
+            y + h * 0.75
+        );
+    }
+}
+
 // Draw a door line onto the pixmap.
 fn draw_door(
     pixmap: &mut Pixmap,

src/layout.rs

@@ -54,6 +54,12 @@ pub struct TextLabel {
     pub font_size: u16,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AreaMarker {
+    pub cell: (usize, usize),
+    pub size: usize,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum WindowSide {
     Left,
@@ -88,6 +94,8 @@ pub struct DungeonLayout {
     pub doors: Vec<Door>,
     pub windows: Vec<Window>,
     pub text_labels: Vec<TextLabel>,
+    pub start_marker: Option<AreaMarker>,
+    pub end_marker: Option<AreaMarker>,
     pub packed_rooms: bool,
 }
 
@@ -99,6 +107,8 @@ impl Default for DungeonLayout {
             doors: Vec::new(),
             windows: Vec::new(),
             text_labels: Vec::new(),
+            start_marker: None,
+            end_marker: None,
             packed_rooms: false,
         }
     }
@@ -166,6 +176,8 @@ pub fn generate_layout(
             doors: Vec::new(),
             windows: Vec::new(),
             text_labels: Vec::new(),
+            start_marker: None,
+            end_marker: None,
             packed_rooms: pack_rooms_without_corridors,
         };
     }
@@ -189,6 +201,8 @@ pub fn generate_layout(
             doors: Vec::new(),
             windows: Vec::new(),
             text_labels: Vec::new(),
+            start_marker: None,
+            end_marker: None,
             packed_rooms: pack_rooms_without_corridors,
         };
     }
@@ -217,6 +231,8 @@ pub fn generate_layout(
             doors: Vec::new(),
             windows: Vec::new(),
             text_labels: Vec::new(),
+            start_marker: None,
+            end_marker: None,
             packed_rooms: true,
         };
         apply_doors(&mut layout, seed, door_settings, cols, rows);
@@ -274,6 +290,8 @@ pub fn generate_layout(
             doors: Vec::new(),
             windows: Vec::new(),
             text_labels: Vec::new(),
+            start_marker: None,
+            end_marker: None,
             packed_rooms: false,
         };
     }
@@ -328,6 +346,8 @@ pub fn generate_layout(
         doors: Vec::new(),
         windows: Vec::new(),
         text_labels: Vec::new(),
+        start_marker: None,
+        end_marker: None,
         packed_rooms: false,
     };
     apply_doors(&mut layout, seed, door_settings, cols, rows);

src/main.rs

@@ -57,6 +57,7 @@ struct DungeonApp {
     hover_corridor_idx: Option<usize>,
     hover_door_idx: Option<usize>,
     hover_text_idx: Option<usize>,
+    hover_marker_kind: Option<MarkerKind>,
 }
 
 impl Default for DungeonApp {
@@ -94,6 +95,7 @@ impl Default for DungeonApp {
             hover_corridor_idx: None,
             hover_door_idx: None,
             hover_text_idx: None,
+            hover_marker_kind: None,
         }
     }
 }
@@ -203,6 +205,8 @@ impl eframe::App for DungeonApp {
                     draw_legend_entry_colorblind(ui, "Secret Doors", LegendStyle::DashDotDotLine);
                     draw_legend_entry_colorblind(ui, "Archways", LegendStyle::DottedLine);
                     draw_legend_entry_colorblind(ui, "Windows", LegendStyle::DashDotLine);
+                    draw_legend_entry_colorblind(ui, "Start Marker", LegendStyle::SolidLine);
+                    draw_legend_entry_colorblind(ui, "End Marker", LegendStyle::SolidLine);
                 } else {
                     draw_legend_entry(ui, Color32::from_rgb(70, 120, 160), "Rooms");
                     draw_legend_entry(ui, Color32::from_rgb(210, 190, 120), "Corridors");
@@ -212,13 +216,15 @@ impl eframe::App for DungeonApp {
                     draw_legend_entry(ui, Color32::from_rgb(170, 80, 170), "Secret Doors");
                     draw_legend_entry(ui, Color32::from_rgb(230, 140, 60), "Archways");
                     draw_legend_entry(ui, Color32::from_rgb(70, 130, 220), "Windows");
+                    draw_legend_entry(ui, Color32::from_rgb(60, 220, 200), "Start Marker");
+                    draw_legend_entry(ui, Color32::from_rgb(240, 90, 90), "End Marker");
                 }
                 ui.add_space(10.0);
                 ui.separator();
                 ui.add_space(8.0);
                 ui.heading("Keybinds");
                 ui.add_space(6.0);
-                ui.label("• Delete / Backspace: Remove hovered room or corridor");
+                ui.label("• Delete / Backspace: Remove hovered room, corridor, door, text, or marker");
                 ui.label("• Ctrl+Z: Undo");
                 ui.label("• Ctrl+Y: Redo");
                 ui.label("• Left click + drag: Move hovered room");
@@ -249,6 +255,7 @@ impl eframe::App for DungeonApp {
                 &self.layout,
                 self.settings.colorblind_mode,
                 self.hover_text_idx,
+                self.hover_marker_kind,
             );
             self.draw_add_overlay(&painter, &geometry);
             self.draw_resize_overlay(&painter, &geometry);
@@ -290,6 +297,7 @@ impl DungeonApp {
         self.hover_corridor_idx = None;
         self.hover_door_idx = None;
         self.hover_text_idx = None;
+        self.hover_marker_kind = None;
         self.pending_delete = false;
     }
 
@@ -323,6 +331,7 @@ impl DungeonApp {
         self.hover_corridor_idx = None;
         self.hover_door_idx = None;
         self.hover_text_idx = None;
+        self.hover_marker_kind = None;
         self.pending_delete = false;
     }
 
@@ -670,6 +679,22 @@ impl DungeonApp {
                     self.settings.add_tool = AddTool::None;
                 }
             }
+            AddTool::StartMarker | AddTool::EndMarker => {
+                self.add_corridor_drag = None;
+                if response.clicked()
+                    && let Some(pointer_pos) = response.interact_pointer_pos()
+                    && let Some((grid_x, grid_y)) = pointer_to_grid(pointer_pos, geometry)
+                {
+                    let cell = (grid_x.floor() as usize, grid_y.floor() as usize);
+                    let kind = match self.settings.add_tool {
+                        AddTool::StartMarker => MarkerKind::Start,
+                        AddTool::EndMarker => MarkerKind::End,
+                        _ => unreachable!(),
+                    };
+                    self.add_marker_at_cell(cell, kind);
+                    self.settings.add_tool = AddTool::None;
+                }
+            }
             AddTool::None => {
                 self.add_corridor_drag = None;
             }
@@ -797,6 +822,26 @@ impl DungeonApp {
         });
     }
 
+    fn add_marker_at_cell(&mut self, cell: (usize, usize), kind: MarkerKind) {
+        if cell.0 >= self.settings.cols || cell.1 >= self.settings.rows {
+            return;
+        }
+
+        let size = match kind {
+            MarkerKind::Start => self.settings.start_marker_size,
+            MarkerKind::End => self.settings.end_marker_size,
+        }
+        .clamp(1, 10);
+        let origin = centered_marker_origin(cell, size, self.settings.cols, self.settings.rows);
+        let marker = layout::AreaMarker { cell: origin, size };
+
+        self.push_undo_snapshot();
+        match kind {
+            MarkerKind::Start => self.layout.start_marker = Some(marker),
+            MarkerKind::End => self.layout.end_marker = Some(marker),
+        }
+    }
+
     // Update which room/corridor/door is currently hovered.
     fn update_hover_targets(&mut self, ctx: &egui::Context, geometry: &GridGeometry) {
         let Some(pointer_pos) = ctx.pointer_hover_pos() else {
@@ -804,6 +849,7 @@ impl DungeonApp {
             self.hover_corridor_idx = None;
             self.hover_door_idx = None;
             self.hover_text_idx = None;
+            self.hover_marker_kind = None;
             return;
         };
         if let Some(edge) = self.door_edge_at_pointer(pointer_pos, geometry) {
@@ -817,12 +863,22 @@ impl DungeonApp {
                 self.hover_room_idx = None;
                 self.hover_corridor_idx = None;
                 self.hover_text_idx = None;
+                self.hover_marker_kind = None;
                 return;
             }
         }
 
         self.hover_text_idx = self.text_at_pointer(pointer_pos, geometry);
         if self.hover_text_idx.is_some() {
+            self.hover_room_idx = None;
+            self.hover_corridor_idx = None;
+            self.hover_door_idx = None;
+            self.hover_marker_kind = None;
+            return;
+        }
+
+        self.hover_marker_kind = self.marker_at_pointer(pointer_pos, geometry);
+        if self.hover_marker_kind.is_some() {
             self.hover_room_idx = None;
             self.hover_corridor_idx = None;
             self.hover_door_idx = None;
@@ -833,14 +889,17 @@ impl DungeonApp {
             self.hover_room_idx = Some(room_idx);
             self.hover_corridor_idx = None;
             self.hover_door_idx = None;
+            self.hover_marker_kind = None;
         } else {
             self.hover_room_idx = None;
             if let Some(corridor_drag) = self.corridor_drag_at_pointer(pointer_pos, geometry) {
                 self.hover_corridor_idx = Some(corridor_drag.corridor_index);
                 self.hover_door_idx = None;
+                self.hover_marker_kind = None;
             } else {
                 self.hover_corridor_idx = None;
                 self.hover_door_idx = None;
+                self.hover_marker_kind = None;
             }
         }
     }
@@ -854,6 +913,20 @@ impl DungeonApp {
             .position(|label| label.cell == clicked)
     }
 
+    fn marker_at_pointer(
+        &self,
+        pointer_pos: egui::Pos2,
+        geometry: &GridGeometry,
+    ) -> Option<MarkerKind> {
+        let (grid_x, grid_y) = pointer_to_grid(pointer_pos, geometry)?;
+        let clicked = (grid_x.floor() as usize, grid_y.floor() as usize);
+        marker_contains_cell(self.layout.start_marker.as_ref(), clicked)
+            .then_some(MarkerKind::Start)
+            .or_else(|| {
+                marker_contains_cell(self.layout.end_marker.as_ref(), clicked).then_some(MarkerKind::End)
+            })
+    }
+
     // Handle right-click resizing of rooms and return whether resizing is active.
     fn handle_resize(
         &mut self,
@@ -1168,6 +1241,15 @@ impl DungeonApp {
             return;
         }
 
+        if let Some(kind) = self.marker_at_pointer(pointer_pos, geometry) {
+            self.push_undo_snapshot();
+            match kind {
+                MarkerKind::Start => self.layout.start_marker = None,
+                MarkerKind::End => self.layout.end_marker = None,
+            }
+            return;
+        }
+
         if let Some(edge) = self.door_edge_at_pointer(pointer_pos, geometry) {
             let target = normalized_edge(edge.0, edge.1);
             if let Some(idx) = self.layout.doors.iter().position(|d| {
@@ -1400,6 +1482,12 @@ enum ResizeCorner {
     BottomRight,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum MarkerKind {
+    Start,
+    End,
+}
+
 #[derive(Debug, Clone)]
 struct RoomResizeState {
     room_idx: usize,
@@ -1491,6 +1579,7 @@ fn draw_layout(
     layout: &DungeonLayout,
     colorblind_mode: bool,
     hover_text_idx: Option<usize>,
+    hover_marker_kind: Option<MarkerKind>,
 ) {
     let wall_width_px = (geometry.cell_size / 5.0).max(1.0);
     let door_width_px = (geometry.cell_size / 10.0).max(1.0);
@@ -1742,6 +1831,29 @@ fn draw_layout(
             color,
         );
     }
+
+    if let Some(marker) = layout.start_marker.as_ref() {
+        draw_area_marker(
+            painter,
+            geometry,
+            marker,
+            "S",
+            Color32::from_rgb(60, 220, 200),
+            colorblind_mode,
+            hover_marker_kind == Some(MarkerKind::Start),
+        );
+    }
+    if let Some(marker) = layout.end_marker.as_ref() {
+        draw_area_marker(
+            painter,
+            geometry,
+            marker,
+            "E",
+            Color32::from_rgb(240, 90, 90),
+            colorblind_mode,
+            hover_marker_kind == Some(MarkerKind::End),
+        );
+    }
 }
 
 // Compute the rectangle for a given grid cell.
@@ -1754,6 +1866,82 @@ fn cell_rect(geometry: &GridGeometry, col: usize, row: usize) -> egui::Rect {
     )
 }
 
+fn marker_rect(marker: &layout::AreaMarker, geometry: &GridGeometry) -> egui::Rect {
+    let left = geometry.rect.left() + marker.cell.0 as f32 * geometry.cell_size;
+    let top = geometry.rect.top() + marker.cell.1 as f32 * geometry.cell_size;
+    egui::Rect::from_min_size(
+        egui::pos2(left, top),
+        egui::vec2(
+            marker.size as f32 * geometry.cell_size,
+            marker.size as f32 * geometry.cell_size,
+        ),
+    )
+}
+
+fn marker_contains_cell(marker: Option<&layout::AreaMarker>, cell: (usize, usize)) -> bool {
+    let Some(marker) = marker else {
+        return false;
+    };
+    cell.0 >= marker.cell.0
+        && cell.0 < marker.cell.0 + marker.size
+        && cell.1 >= marker.cell.1
+        && cell.1 < marker.cell.1 + marker.size
+}
+
+fn centered_marker_origin(
+    cell: (usize, usize),
+    size: usize,
+    cols: usize,
+    rows: usize,
+) -> (usize, usize) {
+    let size = size.clamp(1, 10).min(cols.max(1)).min(rows.max(1));
+    let half = size / 2;
+    let max_x = cols.saturating_sub(size);
+    let max_y = rows.saturating_sub(size);
+    (cell.0.saturating_sub(half).min(max_x), cell.1.saturating_sub(half).min(max_y))
+}
+
+fn draw_area_marker(
+    painter: &egui::Painter,
+    geometry: &GridGeometry,
+    marker: &layout::AreaMarker,
+    label: &str,
+    base_color: Color32,
+    colorblind_mode: bool,
+    hovered: bool,
+) {
+    let rect = marker_rect(marker, geometry);
+    let fill = base_color.gamma_multiply(if colorblind_mode { 0.22 } else { 0.35 });
+    let stroke_color = if hovered {
+        Color32::from_rgb(255, 220, 120)
+    } else if colorblind_mode {
+        Color32::BLACK
+    } else {
+        base_color
+    };
+    let text_color = if colorblind_mode {
+        Color32::BLACK
+    } else {
+        Color32::WHITE
+    };
+    let font_size = (geometry.cell_size * marker.size as f32 * 0.5).clamp(14.0, 72.0);
+
+    painter.rect_filled(rect, 4.0, fill);
+    painter.rect_stroke(
+        rect,
+        4.0,
+        Stroke::new(if hovered { 3.0 } else { 2.0 }, stroke_color),
+        egui::StrokeKind::Middle,
+    );
+    painter.text(
+        rect.center(),
+        egui::Align2::CENTER_CENTER,
+        label,
+        egui::FontId::proportional(font_size),
+        text_color,
+    );
+}
+
 // Draw a rectangular wall segment between two points.
 fn draw_wall_segment(
     painter: &egui::Painter,

src/ui.rs

@@ -8,6 +8,7 @@ enum Tab {
     Generate,
     Layout,
     Add,
+    MonstersAndTraps,
 }
 
 impl Default for Tab {
@@ -131,6 +132,8 @@ pub struct UiSettings {
     pub export_show_grid: bool,
     pub add_tool: AddTool,
     pub add_text_value: String,
+    pub start_marker_size: usize,
+    pub end_marker_size: usize,
     active_tab: Tab,
 }
 
@@ -170,6 +173,8 @@ impl Default for UiSettings {
             export_show_grid: true,
             add_tool: AddTool::None,
             add_text_value: "Text".to_string(),
+            start_marker_size: 1,
+            end_marker_size: 1,
             active_tab: Tab::Generate,
         }
     }
@@ -185,6 +190,8 @@ pub enum AddTool {
     LockedDoor,
     SecretDoor,
     Text,
+    StartMarker,
+    EndMarker,
 }
 
 #[derive(Debug, Clone, Copy, Default)]
@@ -213,6 +220,7 @@ pub fn draw_side_panel(
                 let is_generate = settings.active_tab == Tab::Generate;
                 let is_layout = settings.active_tab == Tab::Layout;
                 let is_add = settings.active_tab == Tab::Add;
+                let is_monsters_and_traps = settings.active_tab == Tab::MonstersAndTraps;
 
                 if ui.selectable_label(is_generate, "Generate").clicked() {
                     settings.active_tab = Tab::Generate;
@@ -223,6 +231,12 @@ pub fn draw_side_panel(
                 if ui.selectable_label(is_add, "Add").clicked() {
                     settings.active_tab = Tab::Add;
                 }
+                if ui
+                    .selectable_label(is_monsters_and_traps, "Monsters & Traps")
+                    .clicked()
+                {
+                    settings.active_tab = Tab::MonstersAndTraps;
+                }
             });
             ui.separator();
 
@@ -230,6 +244,7 @@ pub fn draw_side_panel(
                 Tab::Generate => draw_generate_tab(ui, settings, &mut result, export_in_progress),
                 Tab::Layout => draw_layout_tab(ui, settings, &mut result),
                 Tab::Add => draw_add_tab(ui, settings),
+                Tab::MonstersAndTraps => draw_monsters_and_traps_tab(ui, settings),
             }
         });
 
@@ -744,6 +759,72 @@ fn draw_add_tab(ui: &mut egui::Ui, settings: &mut UiSettings) {
             ui.label("Note: Left click on the canvas to place the text.");
             response
         }
+        AddTool::StartMarker | AddTool::EndMarker => {
+            ui.label("Use the Monsters & Traps tab to place start and end markers.")
+        }
         AddTool::None => ui.label("Select a tool to add rooms or corridors."),
     };
 }
+
+fn draw_monsters_and_traps_tab(ui: &mut egui::Ui, settings: &mut UiSettings) {
+    ui.label(RichText::new("Start / End Markers").strong());
+    ui.add_space(8.0);
+
+    ui.label("Start Marker Size");
+    ui.horizontal(|ui| {
+        ui.add(egui::Slider::new(&mut settings.start_marker_size, 1..=10).show_value(false));
+        ui.add(
+            egui::DragValue::new(&mut settings.start_marker_size)
+                .speed(1.0)
+                .range(1..=10),
+        );
+    });
+
+    ui.add_space(4.0);
+    if ui
+        .selectable_label(settings.add_tool == AddTool::StartMarker, "Place Start Marker")
+        .clicked()
+    {
+        settings.add_tool = if settings.add_tool == AddTool::StartMarker {
+            AddTool::None
+        } else {
+            AddTool::StartMarker
+        };
+    }
+
+    ui.add_space(10.0);
+    ui.label("End Marker Size");
+    ui.horizontal(|ui| {
+        ui.add(egui::Slider::new(&mut settings.end_marker_size, 1..=10).show_value(false));
+        ui.add(
+            egui::DragValue::new(&mut settings.end_marker_size)
+                .speed(1.0)
+                .range(1..=10),
+        );
+    });
+
+    ui.add_space(4.0);
+    if ui
+        .selectable_label(settings.add_tool == AddTool::EndMarker, "Place End Marker")
+        .clicked()
+    {
+        settings.add_tool = if settings.add_tool == AddTool::EndMarker {
+            AddTool::None
+        } else {
+            AddTool::EndMarker
+        };
+    }
+
+    ui.add_space(8.0);
+    match settings.add_tool {
+        AddTool::StartMarker => {
+            ui.label("Click the grid to place the start marker. It is centered on the clicked cell.");
+        }
+        AddTool::EndMarker => {
+            ui.label("Click the grid to place the end marker. It is centered on the clicked cell.");
+        }
+        _ => {
+            ui.label("Monsters, traps, and bosses will live here next. For now, place start and end markers.");
+        }
+    }
+}