View cube TOP and BOTTOM turn the view as little as they can: a click kept forcing heading 0 (front edge at the bottom), so from the back-right iso view TOP spun the model round by 135°. The heading now goes to the nearest quarter turn; halfway between two (an iso view such as home) it takes the one nearer the standard plan view, so home → TOP still has the front at the bottom. The side faces are unchanged (the camera has no roll, so each has one upright view). Tests: nearest_quarter_turn for headings on, near and halfway between quarter turns, and the s39 scenario clicks TOP from the right side and keeps the right side at the bottom

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/book/src/guide/ui-tour.md

@@ -15,7 +15,8 @@
 - **Viewport.** Click to select, Shift or Ctrl to add, drag for a window or crossing box. The
   wheel zooms at the cursor, the middle button pans and Shift+middle orbits (the mouse preset in
   Preferences switches to SolidWorks or Inventor style). The view cube and the navigation bar
-  change the view: a cube face turns to its standard view, an edge to the view halfway between
+  change the view: a cube face turns to look straight at it (TOP and BOTTOM keep the current
+  heading, squared to the nearest quarter turn), an edge to the view halfway between
   its two faces, a chamfered corner to that corner's iso view, and the house goes home. Right-click for the marking menu: eight commands around the cursor, plus a
   menu for whatever is under it.
 - **Dialogs** dock on the right with a live preview. Most features also show drag handles and a