My iPhone 4 is stuck on a black screen

So my iPhone 4 is jailbroken and once I downloaded one tweak it went black. My home button is broken so I have that gesture. Is that what you call it? Whatever it's called it the only thing that is showing in the black screen.

Btw I don't have. Laptop so if your know a way with out one thank you! And don't mind the no grammer. Still learning

Added (1). Oh I forgot to say it was 80%

Plug in your phone to charge it. If it was on low battery before it went black, leave it plugged in for a day or overnight.

if it doesn't work after that, try holding down the home button and the lock button (the one on the top), for about ten seconds, or until if a Apple logo appears on the screen.

if that doesn't work, and you don't have a computer with iTunes installed synced to your iPhone to reset it back to factory settings, you maybe out of luck and either take it to an Apple store if there's one nearby, or you may need to get a new phone all together.

Once you have jailbroken a phone, it's anybody's guess as to how to fix it, if it can be fixed at all. It's a big risk when you jailbreak without knowing what you're doing -- or how to recover if things go wrong.