I stood at the squat rack, barbell loaded, trying to do math. 45 lbs on each side, times two, plus the bar… Is that 135? 140? I could never get it right. Plus: My training app logs my weights in kilograms, so now I had to convert on top of that. I stared at the ceiling, punched numbers into my phone calculator, gave up, and logged “heavy.” That was my life for two years. Then one evening, in about twenty minutes, I built an app that fixed it. The app was embarrassingly simple: It adds up the total weight of the barbell plates I was lifting, and gives it to me in kilograms and in pounds. No social features, no cloud sync, not even a login. Just a weight calculator app for my gym. For something that took twenty minutes to build, I was stupidly proud of it. It started at a workshop...