METRO.CO.UK - Aug 24 - Engineer David Minns is known for creating dating apps with a twist. In February, he launched Butterfly, a transgender dating app that stops offensive terms being used within messages with the help of an auto-correction tool. A month later came Dinky One - a dating app for men who have small or micro penises. His latest invention is 20Dating, an app where users are only able to match with people who are 20 years older or younger.