How do I get out of here?

We have had the playpen downstairs and William has for a few weeks now enjoyed playing in there for very brief time periods, long enough for me to make sandwiches or use the bathroom without worrying about what he is eating from the floor. But recently William has been eager to start walking and prefers to spend his play time cruising around and climbing up furniture. Last week he was trying to get out of the playpen by smushing himself up against the mesh and forcefully trying to push his way out. I think he has figured it out. Now he is trying to climb out ;)