diff --git a/editor/src/plugins/color_picker.rs b/editor/src/plugins/color_picker.rs
index 636251ed81..0d80a81efa 100644
--- a/editor/src/plugins/color_picker.rs
+++ b/editor/src/plugins/color_picker.rs
@@ -1,6 +1,7 @@
 // Copyright 2018 Google LLC, licensed under http://www.apache.org/licenses/LICENSE-2.0
 
 use ezgui::{Canvas, Color, GfxCtx, InputResult, Menu};
+use geom::Polygon;
 use objects::{Ctx, SETTINGS};
 use piston::input::Key;
 use plugins::{Plugin, PluginCtx};
@@ -102,9 +103,9 @@ impl Plugin for ColorPicker {
                             (x * TILE_DIMS + start_x) as f64,
                             (y * TILE_DIMS + start_y) as f64,
                         ));
-                        g.draw_rectangle(
+                        g.draw_polygon(
                             color,
-                            [corner.x(), corner.y(), TILE_DIMS as f64, TILE_DIMS as f64],
+                            &Polygon::rectangle_topleft(corner, TILE_DIMS as f64, TILE_DIMS as f64),
                         );
                     }
                 }
diff --git a/editor/src/plugins/show_activity.rs b/editor/src/plugins/show_activity.rs
index e6eded5167..a9b817a4df 100644
--- a/editor/src/plugins/show_activity.rs
+++ b/editor/src/plugins/show_activity.rs
@@ -1,5 +1,5 @@
 use ezgui::{Color, GfxCtx};
-use geom::{Bounds, Pt2D};
+use geom::{Bounds, Polygon, Pt2D};
 use objects::{Ctx, DEBUG};
 use piston::input::Key;
 use plugins::{Plugin, PluginCtx};
@@ -112,14 +112,16 @@ impl Heatmap {
                 let percent = (self.counts[x][y] as f32) / (self.max as f32);
                 // TODO Map percent to hot/cold colors. For now, don't ever become totally opaque.
                 let color = Color::rgba(255, 0, 0, percent * 0.8);
-                g.draw_rectangle(
+                g.draw_polygon(
                     color,
-                    [
-                        self.bounds.min_x + (x as f64) * tile_width,
-                        self.bounds.min_y + (y as f64) * tile_height,
+                    &Polygon::rectangle_topleft(
+                        Pt2D::new(
+                            self.bounds.min_x + (x as f64) * tile_width,
+                            self.bounds.min_y + (y as f64) * tile_height,
+                        ),
                         tile_width,
                         tile_height,
-                    ],
+                    ),
                 );
             }
         }
diff --git a/editor/src/render/intersection.rs b/editor/src/render/intersection.rs
index ade149308d..e37440689b 100644
--- a/editor/src/render/intersection.rs
+++ b/editor/src/render/intersection.rs
@@ -52,14 +52,9 @@ impl DrawIntersection {
     fn draw_traffic_signal(&self, g: &mut GfxCtx, ctx: Ctx) {
         let radius = 0.5;
 
-        g.draw_rectangle(
+        g.draw_polygon(
             ctx.cs.get("traffic signal box", Color::BLACK),
-            [
-                self.center.x() - (2.0 * radius),
-                self.center.y() - (4.0 * radius),
-                4.0 * radius,
-                8.0 * radius,
-            ],
+            &Polygon::rectangle(self.center, 4.0 * radius, 8.0 * radius),
         );
 
         g.draw_circle(
diff --git a/ezgui/src/lib.rs b/ezgui/src/lib.rs
index c36c3c7dd9..23b4fd06ba 100644
--- a/ezgui/src/lib.rs
+++ b/ezgui/src/lib.rs
@@ -138,16 +138,6 @@ impl<'a> GfxCtx<'a> {
             self.gfx,
         );
     }
-
-    // TODO probably better to have a Polygon::make_rectangle helper or something
-    pub fn draw_rectangle(&mut self, color: Color, rect: [f64; 4]) {
-        graphics::Rectangle::new(color.0).draw(
-            rect,
-            &self.ctx.draw_state,
-            self.ctx.transform,
-            self.gfx,
-        );
-    }
 }
 
 pub struct ToggleableLayer {
diff --git a/geom/src/polygon.rs b/geom/src/polygon.rs
index e7bce4099c..c65b32a896 100644
--- a/geom/src/polygon.rs
+++ b/geom/src/polygon.rs
@@ -164,6 +164,28 @@ impl Polygon {
                 .collect(),
         )
     }
+
+    pub fn rectangle(center: Pt2D, width: f64, height: f64) -> Polygon {
+        let (x, y) = (center.x(), center.y());
+        let half_width = width / 2.0;
+        let half_height = height / 2.0;
+        Polygon::new(&vec![
+            Pt2D::new(x - half_width, y - half_height),
+            Pt2D::new(x + half_width, y - half_height),
+            Pt2D::new(x + half_width, y + half_height),
+            Pt2D::new(x - half_width, y + half_height),
+        ])
+    }
+
+    pub fn rectangle_topleft(top_left: Pt2D, width: f64, height: f64) -> Polygon {
+        let (x, y) = (top_left.x(), top_left.y());
+        Polygon::new(&vec![
+            Pt2D::new(x, y),
+            Pt2D::new(x + width, y),
+            Pt2D::new(x + width, y + height),
+            Pt2D::new(x, y + height),
+        ])
+    }
 }
 
 #[derive(Clone, Debug)]
diff --git a/synthetic/src/model.rs b/synthetic/src/model.rs
index 30eb21de1a..f35db8e2f5 100644
--- a/synthetic/src/model.rs
+++ b/synthetic/src/model.rs
@@ -42,19 +42,12 @@ impl Road {
 }
 
 pub struct Building {
-    top_left: Pt2D,
+    center: Pt2D,
 }
 
 impl Building {
     fn polygon(&self) -> Polygon {
-        let (x, y) = (self.top_left.x(), self.top_left.y());
-
-        Polygon::new(&vec![
-            Pt2D::new(x, y),
-            Pt2D::new(x + BUILDING_LENGTH, y),
-            Pt2D::new(x + BUILDING_LENGTH, y + BUILDING_LENGTH),
-            Pt2D::new(x, y + BUILDING_LENGTH),
-        ])
+        Polygon::rectangle(self.center, BUILDING_LENGTH, BUILDING_LENGTH)
     }
 }
 
@@ -143,13 +136,13 @@ impl Model {
 }
 
 impl Model {
-    pub fn create_b(&mut self, top_left: Pt2D) {
+    pub fn create_b(&mut self, center: Pt2D) {
         let id = self.buildings.len();
-        self.buildings.insert(id, Building { top_left });
+        self.buildings.insert(id, Building { center });
     }
 
-    pub fn move_b(&mut self, id: IntersectionID, top_left: Pt2D) {
-        self.buildings.get_mut(&id).unwrap().top_left = top_left;
+    pub fn move_b(&mut self, id: IntersectionID, center: Pt2D) {
+        self.buildings.get_mut(&id).unwrap().center = center;
     }
 
     pub fn remove_b(&mut self, id: BuildingID) {