Level Design Video Tutorials - Valve Developer Community
Former Valve developer shares his toxic experience while working on 'Source 2'. He criticises the whole project while saying "This was the most toxic group of developers I've ever seen." : r/esports
Getting Started - Valve Developer Community
Orphaned Source SDK Content | Valve Developer Union
Source Filmmaker - Valve Developer Community
BSPSource - Valve Developer Community
Steam Deck: Five big things we learned from Valve's developer summit - The Verge