First, what is the game-mode?
Stuka is a gamemode where there is a place of combat and the random chance a person will appear in the sky and carpet bomb what is below and in maps prefix terms its written as stka_(mapname)
I created this gamemode by creating a couple of maps and uploading them to the Steam workshop for Garry's Mod and posting around general forums
The first three maps to be uploaded were
stka_nervepit - Floating arena with a red pentagon nerve filled with nerve gas, surrounded in metal links, having 2 dumpster bases and a nice soundscape
stka_sansbox - Snowy Arena with a questionable sans gas chamber and arena rim.
stka_mutaharcube - Arena with four quadrants and a large tower having two ladders with a giant cube featuring the youtuber 'Mutahar' from the youtube channel SomeOrdinaryGamers
Now how do you make the 'stuka' function in a way where its random and someone drops down?
Its not hard, create a small brush high in the skybox, put a trigger_hurt on top with a info_player_start (start is instead deathmatch in HL2DM's SDK just a formality sort o thing)
You can balance the trigger_hurt's damage and type your self, make sure you give it A NAME since it will help you with basic trigger outputs and such. Name it stukatrigger or something like that
Now add an ambient_generic on the brush and a game_text
Go to the trigger in its outputs section add two of them then set them to OnStartTouch for both then the names of the game_text and ambient_generic or use the cool picker tool to just poke em. Now you can use a custom sound that plays to the stuka or for everyone (if you activate the flag)
The sound I normally use thats pretty much just stuck with it is the Battle 1 theme from Lords of the Realm II why? was listening to it while making it and it fits I guess. Again, you can set this to play to everyone but I normally like just the radius of the stuka's spawn.
Now for his equipment, EASY! Just put 3 smg1 grenades a stun stick and some armour to make em formidable.
Thats pretty much the method of making a stuka map
My favorite map is "nervepit" because it had a nice soundscape and had room to relax in the bases with a lil radio you can try to implement it yourself by using a env_soundscape and going to the Valve Dev Wiki and picking the one you like :)
then in the game_text edit the colors to your liking and write in the field something like "stuka is here" or "stuka time" activate in its flags to be broadcasted to everyone.
Now when the stuka spawns music plays and everyone is alerted.
I hope this tutorial was of use to you, enjoy!