1. ballet 指“芭蕾舞”，是不可数名词。之前加冠词 a 后，表示“一种芭蕾舞剧”，变得可数。

N-COUNT（可数名词） A ballet is an artistic work that is performed by ballet dancers. 芭蕾舞剧

The performance will include the premiere of three new ballets.

这次演出将包括3部新芭蕾舞剧的首演。

2. of shape and space 是定语。

present a ballet of shape and space

意思是：呈现一种具有形状感和空间感的芭蕾舞剧。