Phoebe has now reached 1yr old

We have a stair gate to keep her in the kitchen when we're not there and at night (no door - just an arch way). But..........the last couple of days she has jumped over the gate

. She's not done any damage but there's still time

. I'm a bit worried that she might wreck things if she can't get to her toys.
I don't know whether to see how we go or invest in a play pen. But I suppose if she jumps the stair gate she'll get out of the pen

.
Any ideas?