Creative Restrictions

It may seem like an oxymoron to you, the idea of creative restrictions, but it’s actually not. The imagination, to be at full power, seems to require some parameters or restrictions. For example: if I tell a class of art students to paint anything at all on their blank canvas, the results are not as interesting or dynamic as when some sort of guidelines are given. These restrictions can be as simple as: use only 2 colours, or express in paint the emotion of joy. These minimal parameters become a spark to the fuel of creativity. Of course too many restrictions are not good either. Like too much salt, they can spoil the creative stew too. What kind of restrictions spark your creative mode?