If you continue deving the game maybe shade in some of the jump scare comic-book-like-square art, change up the music per room you explore, customize the GUI a bit more. I thought the phone was unique and would do well to be flushed out more for interactivity. Also, make more things explorable per room!
Having the phone act as more of a "You're getting warmer" mechanic could be cool too. Like: the cellphone stays on screen the whole time and those animations show if you're "closer" to the doll or not when you enter a room. Maybe even make the choices be selected from the phone itself or a built-out/stylized soze panel on the screen.
Or consider adding a health mechanic where you run into more traps or wrong locations and you lose health. I'm thinking like how resident evil visualized health. It could be a static image or series of images that animate on screen with a repeat line.