Guidelines for square faces:

1. It is best to wear oval sunglasses for square faces. Square and round frames will highlight the lines of a square face and should be avoided.

2. The popular oversized sunglasses are not suitable for square faces. It is best to choose a style with delicate flat round frames and delicate temples to soften the lines of the face.

3. Choose sunglasses that fit snugly and cover your face to modify your face shape.

Guidelines for round faces:

1. Do not choose sunglasses with round frames, as they will make your face look rounder.

2. It is recommended to choose a style with a slightly raised end of the frame.

3. It is best to choose a thinner spectacle frame to avoid magnifying the round face.

Guidelines for long faces:

1. Large-frame sunglasses are suitable and can make your face look shorter.

2. You can consider angular frames to modify your face shape and make the outline more natural.

3. It is best to choose a wide version of the spectacle stand, which can create the visual effect of shortening the face.