Sentence:  Thus shielded , we played many foolish games in comfortable unselfconsciousness ; even when the fences <WSD>became</WSD> a part of the game - when a vine embowered gate-post was the Sleeping Beauty 's enchanted castle , or when Rapunzel let down her golden hair from beneath the crocketed spire , even then we paid little heed to those who went by on the path outside . 
Meaning of the word marked with <WSD> tags:  undergo a change or development