Level Editor (Early Access 11.0)

This week I've been working exclusively on the level editor, so all the changes here pertain to that.

• Decoupled level editor state from game state
• 3D walls and lighting are no longer drawn when editing
• You can pan in edit mode by holding the middle mouse button
• You can zoom in edit mode by holding shift and scrolling
• Added wall texture selector
• Selected object in edit mode is shown on cursor
• Added exit toolbox with exit lock toggle
• You can change the start point of a level by placing Flint
• Added an X button to close toolboxes