Good job with the basics.
May I suggest you check out these?
1. https://developer.valvesoftware.com/wiki/Hammer_Hotkey_Reference
2. https://developer.valvesoftware.com/wiki/List_of_entities
3. https://developer.valvesoftware.com/wiki/Sky_List
4. https://developer.valvesoftware.com/wiki/Sound_and_Music
5. https://developer.valvesoftware.com/wiki/Breakable_Glass
6. https://developer.valvesoftware.com/wiki/Beams_and_Lasers
7. https://developer.valvesoftware.com/wiki/Dust,_Fog,_%26_Smoke
8. https://developer.valvesoftware.com/wiki/Fire
9. https://developer.valvesoftware.com/wiki/Cables_and_Ropes