Added note on rotating collision shapes

docs/en/manuals/physics.md

@@ -136,6 +136,15 @@ The shape will not be drawn in the editor. You can [enable Physics debugging](/m
 It is possible to let the collision object and its shapes inherit the scale of the game object. Check the [Allow Dynamic Transforms](/manuals/project-settings/#allow-dynamic-transforms) checkbox in the Physics section of *game.project* to enable this. Note that only uniform scaling is supported and that the smallest scale value will be used if the scale isn't uniform.
 
 
+### Rotating collision shapes
+
+#### Rotating collision shapes in 3D physics
+Collision shapes in 3D physics can be rotated around all axis.
+
+#### Rotating collision shapes in 2D physics
+Collision shapes in 2D physics can only be rotated around the z-axis. Rotation around the x or y axis will yield incorrect results and should be avoided, even when rotating 180 degrees to essentially flip the shape along the x or y axis. To flip a physics shape it is recommended to use [`physics.set_hlip(url, flip)`](/ref/stable/physics/?#physics.set_hflip:url-flip) and [`physics.set_vlip(url, flip)`](/ref/stable/physics/?#physics.set_vflip:url-flip).
+
+
 ### Units used by the physics engine simulation
 
 The physics engine simulates Newtonian physics and it is designed to work well with meters, kilograms and seconds (MKS) units. Furthermore, the physics engine is tuned to work well with moving objects of a size in the 0.1 to 10 meters range (static objects can be larger) and by default the engine treats 1 unit (pixel) as 1 meter. This conversion between pixels and meters is convenient on a simulation level, but from a game creation perspective it isn't very useful. With default settings a collision shape with a size of 200 pixels would be treated as having a size of 200 meters which is well outside of the recommended range, at least for a moving object. In general it is required that the physics simulation is scaled for it to work well with the typical size of objects in a game. The scale of the physics simulation can be changed in `game.project` via the [physics scale setting](/manuals/project-settings/#physics). Setting this value to for instance 0.02 would mean that 200 pixels would be treated as a 4 meters. Do note that the gravity (also changed in `game.project`) has to be increased to accommodate for the change in scale.