Managing a dwindling light source in an abandoned hospital is a classic tension engine, and the idea that every blackout brings you closer to the truth gives it a nice hook. Light being your only protection while the power slowly runs out is an easy-to-grasp and creepy premise.
I'd also be so happy if you could check out my entry, Forever. It's Valentine's-week dating-app dread in about 10 minutes, with two endings. Honest ratings and feedback are really appreciated, and thanks for reading!