The floor shifting, as if a floorboard were about to give way. The horizon moving up and down, as if bobbing in a small boat at sea or driving along a corrugated dirt road. Migraine-warning visual interference, without the headache. These are memories of sensations on seeing Bridget Riley’s paintings. The huge ones, which fill your field of vision. As I look, suddenly, the lines and colours, which had been static patterns, start to shimmer, to dance. Artistic magic. Trying to read the words of yesterday’s art quote gives a glimmer of the shimmering sensation; to my eyes anyway.