in a single player map im working on, im trying to add checkpoints where the game saves itself. i've seen some tutorials and it tells me to type 9game_save) in my scripts. but how do i make it so say i was walking in a tunnel. i want to save at a certain point inside the tunnel. how do i do that.

you know how to script? if yes, then you need to place a trigger volume where you want it to save, which you script that it detects if the player is on trigger, then it saves.

To add on to his point: DO NOT USE GAME_SAVE

What game_save does is that it checks for enemies around the player withing a certain radius. It will check for 8 seconds, and if they’re still enemies, it will give up. However, using this command: game_save_no_timeout is better, as the game will never stop checking, and will eventually save a checkpoint.

Or you could try game_save_totally unsafe, which will save the checkpoint no matter what happens, even if the player has only 1 health bar left and is surronded by 20 elites 0_o

Which is why you use game_save_totally_unsafe. NOTE: game_save and game_save_no_timout ONLY WORK if the player isn't moving. If you're walking, it won't work. Bungie themselves used game_save_totally_unsafe to save. They only used game_save right after a cutscene, because it wasn't likely that you would move as soon as it ended.

TL;DR version
Use game_save_totally_unsafe, but only if there are no enemies. Which in your scenario, it should work. So create a trigger volume called tvol, and put it where the player will walk. Add this to your script:

(script startup tvol
(sleep_until (volume_test_objects tvol (players)) 15)
(game_save_no_timeout)
)