How parallel do these lines appear?

This square seems to be suffering on this background

Another set of parallel lines distorted by the background

This series of concentric slanted lines leads the eye towards the centre in the manner of a spiral.

This is the famous "cafe wall" illusion discovered here in Bristol at the bottom of St Michael's Hill.

Click on the sides of the picture to slide the tiles left or right relative to each other.

Investigate the effect of the mortar brightness by clicking at the top or bottom of the picture.

Which combination gives the most dramatic effect for you?

Shape can be disguised by combinations of colour and texture that mirror the background - camouflage.

Can you find a recognisable object in this picture?