Booklet for learning highway code - has questions with answers hidden in mixture of dots and dashes and revealed through coloured film

摘要

The booklet has its page divided into vertical columns, the first comprising set questions on the highway code. The adjoining column has several answers to each question, the pupil selecting one as the correct reply. The next column shows the correct answer for each question, this being hidden by an optical illusion formed by a mixture of dots and dashes, the former being dark blue or black and the latter red. When a red coloured transparent film is placed over the column, the dots are emphasised and the correct reply read.