My kids are my toughest playtesters.

My oldest is seven and my youngest is four, and neither of them has any patience for a loading screen. If a game does not respond in the first few seconds, they hand the tablet back and go find the crayons. It is the most honest usability test I have ever run.

The first version of the dinosaur game had a menu. Start, settings, a little credits screen I was proud of. My youngest pressed the dinosaur on the title art four times, decided it was broken, and wandered off. Now the title art is the game. You tap the dinosaur, it roars, and you are playing.

Kids do not read instructions, so everything has to explain itself through what happens when you poke it. That turns out to be a great rule for grown-up software too. If a feature needs a paragraph of help text, the feature is usually the problem.

They are also merciless about consistency. If the jump button is on the left in one level and on the right in the next, I hear about it immediately, and loudly. Adults just quietly get worse at using your app and blame themselves.

The best moments are the ones I did not plan. My oldest discovered that if you make the triceratops sneeze three times in a row it does a little spin. That was a bug. It is now a feature with its own sound effect, because she was so delighted by it.

I build these games because I want my daughters to grow up seeing that the things on their screens were made by people, and that they could make them too. The lesson that keeps coming back to me is simpler: watch real people use the thing, and believe what you see.