so i havent messed with source sdk in a couple years and today i decided to open up a few old projects. only thing is now it only gives me the option to map for episode 2, portal, and TF2. how do i get my HL2DM back so i can map for it? i remember back in the day you had to launch the game first for it to show up but thats not doing anything here. i tried to configure it manually but that definitely didnt work. any help please?