Interesting use of PROPORTION. Cutting it off at the floor and ceiling and walls of the room makes the FORM much more interesting than if it was just a common jungle-gym. Having this as an indoor piece also makes an interesting use if SPACE. It is reminiscent of an outdoor toy that the viewer wants to climb on and inside, yet we can't see the whole piece. It appears to continue outside of the room we see and we know what it would look like whole, but it isn't actually there.