You'll need to hold the power button for a long time eventually the soft keys will blink,and it will reset. When it turns off to reboot,start holding vol down and you should be able to fix the issue.
We need more info on what happened prior to the non-boot situation. Had you tried to flash a Rom? Unfortunately,"no idea what I did" does not give us an obvious clue to the issue,and therefore its difficult to offer a solution without going thru a long list of possabilities
The Delivery Guy
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