DLDI (Dynamically Linked Device Interface) files for Nintendo DS homebrew files that allow them to fully communicate with the flash cart device they are running on.
These are generally no longer needed as flash cart manufacturers commonly incorporate automatic DLDI patching in to the system firmware/loader.
Only thing drive me crazy is all these new horror games nowadays is its so dark, all time. I can't even play them. I understand they trying to create spooky but be creative a little, not just darkness with pop out scare scenes.