im going out of my mind

so the past few nights have been a nightmare. Cadence has been sleeping in a toddler bed for awhile now but just recently relized she can get up when ever she wants. We have also changed bed time around since she was waking up so early we wanted her to sleep a little later so we moved bed time from sevenish to around 8:30 9:00. But now when I put her down and shut the door she immediatly gets up and comes to the door and walks out. I put her back down and we start again. This goes on for about an hour. She thinks this is a game so nothing I say or do makes her understand stay in the bed. I tell her she will go to time out but that just meens i get to get up. I tell her she will get in trouble and she has to stay in bed. I get very frustrated and im not sure what to do about it. We ahve decided not to spank because how can we tell her not to hit and then do what we tell her not to do? so im out of options. Im hoping and praying this is just a phase and in a week or two she will grow out of it. i don't think anyone who reads this has children but if you do and have any advice I would love it:)