[{"_id":ObjectId("628be38c81f6e31196b6148b"),"items":[{"shape":"circle","color":"blue"},{"shape":"square","color":"red"},{"shape":"triangle","color":"yellow"}]}]

db.collection.aggregate([{$unwind:"$items"},{$match:{"items.shape":"circle"}},{$project:{"_id":0,"color":"$items.color","shape":"$items.shape"}}])