Special mouse clicking combinations

     A + right mouse click: Add actor there. 
     L + right mouse click: Add light there. 

Shortcut keys

     Delete: Delete selected actors. 
     1, 2, 3: Slow, medium, and fast movement speed. 
     F1: Help. 
     F4: Actor properties. 
     F5: Surface properties. 
     F6: Level properties. 
     F7: Compile changed scripts. 
     F8: Rebuilder. 
     B: Toggle brush visibility in the current viewport. 
     H: Toggle actor visibility in the current viewport. 
     P: Toggle player controls or realtime update of the viewport. 
     Shift-A: Select all actors. 
     Shift-B: Select all surfaces belonging to the selected surfaces' brushes. 
     Shift-C: Select adjacent coplanar polygons. 
     Shift-D: Duplicate selected actors. 
     Shift-F: Select adjacent floors. 
     Shift-G: Select surfaces belonging to the selected surfaces' groups. 
     Shift-I: Select surfaces with items matching the selected surfaces' items. 
     Shift-J: Select all adjacent surfaces(flood-fill). 
     Shift-L: Look ahead in the current viewport (no pitch or roll). 
     Shift-M: Memorize selected surfaces. 
     Shift-N: Select none. 
     Shift-O: Select surfaces from intersection of selected surfaces and memory. 
     Shift-P: Select all surfaces. 
     Shift-Q: Reverse the set of selected surfaces. 
     Shift-R: Recall memorized surface selection. 
     Shift-T: Select all surfaces which use the current texture. 
     Shift-U: Select union of selected surfaces and memorized surfaces. 
     Shift-W: Select adjacent wall surfaces (flood-fill). 
     Shift-X: Select exclusive or of selected surfaces and memorized surfaces. 
     Shift-Y: Select adjacent slanted surfaces. 
     Shift-Z: Select none. 
     Ctrl-A: Add brush to world. 
     Ctrl-B: Load brush. 
     Ctrl-C: Copy. 
     Ctrl-D: Deintersect brush with world. 
     Ctrl-E: Save as. 
     Ctrl-L: Save level. 
     Ctrl-O: Load level. 
     Ctrl-P:  Play level. 
     Ctrl-N: Intersect brush with world. 
     Ctrl-R: Redo. 
     Ctrl-S: Subtract brush from world. 
     Ctrl-V: Paste. 
     Ctrl-W: Duplicate. 
     Ctrl-X: Cut. 
     Ctrl-Z: Undo.