diff --git a/crates/ui-egui/src/panels/properties/tests.rs b/crates/ui-egui/src/panels/properties/tests.rs
--- a/crates/ui-egui/src/panels/properties/tests.rs
+++ b/crates/ui-egui/src/panels/properties/tests.rs
@@ -1,4 +1,5 @@
 use egui::{Event, PointerButton, Pos2, Rect, vec2};
+use serde_json::Value;
 use vectorcraft_engine::Session;
 
 use super::*;
@@ -1428,3 +1429,114 @@ fn one_effect_has_a_delete_icon_in_appearance() {
     app.run("select.set", json!({"ids": [id, other]})).unwrap();
     assert!(!shows(&tall(&mut app, &ctx, vec![]), &name), "two objects");
 }
+
+/// A rectangle at 100, 100, 100 × 60 pt, selected, with `then` run on it, and a context that
+/// builds the accessibility tree (to find the locator's squares).
+fn reference_setup(then: &[(&str, Value)]) -> (VectorcraftApp, egui::Context) {
+    let mut app = VectorcraftApp::new(Session::new(), Default::default());
+    app.run("file.new", json!({"width": 300, "height": 300})).unwrap();
+    app.run("shape.rectangle", json!({"x": 100, "y": 100, "width": 100, "height": 60})).unwrap();
+    for (id, p) in then {
+        app.run(id, p.clone()).unwrap();
+    }
+    let ctx = egui::Context::default();
+    crate::theme::install_fonts(&ctx);
+    ctx.enable_accesskit();
+    (app, ctx)
+}
+
+/// Clicks the topmost control of `draw` that screen readers call `name`.
+fn click_named(app: &mut VectorcraftApp, ctx: &egui::Context, draw: fn(&mut VectorcraftApp, &mut Ui), name: &str) {
+    let mut out = ctx.run_ui(egui::RawInput::default(), |ui| draw(app, ui));
+    out.textures_delta.clear();
+    let nodes = &out.platform_output.accesskit_update.as_ref().expect("an accessibility tree").nodes;
+    let b = nodes
+        .iter()
+        .filter(|(_, n)| n.label() == Some(name))
+        .filter_map(|(_, n)| n.bounds())
+        .min_by(|a, b| a.y0.total_cmp(&b.y0))
+        .unwrap_or_else(|| panic!("no {name:?}"));
+    let at = egui::pos2(((b.x0 + b.x1) / 2.0) as f32, ((b.y0 + b.y1) / 2.0) as f32);
+    crate::panels::tests_appearance::click(ctx, app, at, draw);
+}
+
+/// Types `value` over the topmost field of `draw` that shows `shown`, and presses Enter.
+fn type_over(app: &mut VectorcraftApp, ctx: &egui::Context, draw: fn(&mut VectorcraftApp, &mut Ui), shown: &str, value: &str) {
+    use crate::panels::tests_appearance::{click, frame_events, text_rect};
+    let texts = frame_events(ctx, app, vec![], draw);
+    click(ctx, app, text_rect(&texts, shown).center(), draw);
+    let key = |key, modifiers| Event::Key { key, physical_key: None, pressed: true, repeat: false, modifiers };
+    frame_events(ctx, app, vec![key(egui::Key::A, egui::Modifiers::COMMAND)], draw);
+    frame_events(ctx, app, vec![Event::Text(value.into())], draw);
+    frame_events(ctx, app, vec![key(egui::Key::Enter, egui::Modifiers::NONE)], draw);
+    frame_events(ctx, app, vec![], draw);
+}
+
+/// The Properties panel with the Transform panel below it, as when both are open.
+fn properties_and_transform(app: &mut VectorcraftApp, ui: &mut Ui) {
+    show(app, ui);
+    ui.separator();
+    crate::panels::transform::show(app, ui);
+}
+
+/// A panel (or panels) drawn in a test frame.
+type Draw = fn(&mut VectorcraftApp, &mut Ui);
+
+fn near(a: vectorcraft_geom::Point, b: vectorcraft_geom::Point) -> bool {
+    (a - b).hypot() < 1e-6
+}
+
+/// #4285: with the locator's top-left square chosen, a rotation typed in the Properties panel's
+/// Transform section turns the selection about the box's top-left corner, as the Transform panel
+/// does: on a plain rectangle, on one already turned 30°, and with the Transform panel open too.
+#[test]
+fn a_typed_rotation_turns_about_the_reference_point() {
+    // (case, the angle the rectangle starts at, the panels, the angle typed)
+    let cases: [(&str, f64, Draw, &str); 4] = [
+        ("section", 0.0, transform_section, "45"),
+        ("panel", 0.0, show, "45"),
+        ("turned 30°", 30.0, transform_section, "60"),
+        ("with the Transform panel", 0.0, properties_and_transform, "45"),
+    ];
+    for (case, start, draw, value) in cases {
+        let (mut app, ctx) = reference_setup(&[("object.rotate", json!({"angle": start}))]);
+        let shown = format!("{start}°");
+        click_named(&mut app, &ctx, draw, "Top Left");
+        assert_eq!(ctx.data(|d| d.get_temp::<usize>(egui::Id::unique("refpt"))), Some(0), "{case}: the locator's choice");
+        let corner = app.selection_box().unwrap().reference_point(0);
+        type_over(&mut app, &ctx, draw, &shown, value);
+        let bx = app.selection_box().unwrap();
+        assert!((bx.angle - value.parse::<f64>().unwrap()).abs() < 1e-6, "{case}: turned to {}", bx.angle);
+        assert!(near(bx.reference_point(0), corner), "{case}: the top-left corner {corner:?} moved to {:?}", bx.reference_point(0));
+    }
+}
+
+/// #4285: the flip buttons mirror the selection about the chosen reference point: with the
+/// top-left square, across the box's left edge (left-right) or top edge (top-bottom).
+#[test]
+fn the_flip_buttons_mirror_about_the_reference_point() {
+    for (button, want) in [("Flip Along Horizontal Axis", (0.0, 100.0, 100.0, 160.0)), ("Flip Along Vertical Axis", (100.0, 40.0, 200.0, 100.0))] {
+        let (mut app, ctx) = reference_setup(&[]);
+        click_named(&mut app, &ctx, transform_section, "Top Left");
+        click_named(&mut app, &ctx, transform_section, button);
+        let r = app.selection_box().unwrap().rect;
+        let got = (r.x0, r.y0, r.x1, r.y1);
+        assert!([got.0 - want.0, got.1 - want.1, got.2 - want.2, got.3 - want.3].iter().all(|d| d.abs() < 1e-6), "{button}: {got:?}, want {want:?}");
+    }
+}
+
+/// With Use Registration Point for Symbol on, one symbol instance turns about its symbol's
+/// registration point (here the bottom-right one) whatever the locator shows: the locator
+/// follows the registration point.
+#[test]
+fn a_symbol_instance_turns_about_its_registration_point() {
+    let (mut app, ctx) = reference_setup(&[]);
+    let id = app.run("symbol.new", json!({"name": "Corner", "registration": 8})).unwrap()["id"].clone();
+    app.run("select.set", json!({"ids": [id]})).unwrap();
+    app.session.prefs.use_registration_point_for_symbol = true;
+    click_named(&mut app, &ctx, transform_section, "Top Left");
+    type_over(&mut app, &ctx, transform_section, "0°", "45");
+    let bx = app.selection_box().unwrap();
+    assert!((bx.angle - 45.0).abs() < 1e-6, "turned to {}", bx.angle);
+    assert!(near(bx.reference_point(8), vectorcraft_geom::Point::new(200.0, 160.0)), "the registration point moved to {:?}", bx.reference_point(8));
+}