请分析下面这个句子的语法结构： "Despite working hard all day, I did not complete the project on time."
这个句子的主语是"I"，谓语动词是"did not complete"，"Despite working hard all day"是状语从句，表示原因。整个句子是一个复合句，主句是"I did not complete the project on time"，从句是"Despite working hard all day"。