Map editor! I added an editor bool to the global engine state and that controls whether the editor GUI is drawn and whether the player system runs or not. I also added some stuff like moving objects by clicking on them and adding stuff to the scene like grass blades. The way that the mouse to world space conversion works is that the cursor position is multiplied with the inverse of the projection matrix and this gives a direction in world space which is used as a raycast and if it hits anything, the object will be spawned at the hit position.