Our biggest challenge wasn't technical, it was philosophical. We started assuming Flow was "good" and Drag was "bad," but the research, including Csikszentmihalyi's own warnings about flow addiction, flipped that framing completely. Designing for ADHD users whose experience we don't share added another layer: everyone we talked to had different symptoms at different strengths, so there was no single user to design for, and the biometric sensing model was our answer to staying accurate without nagging people who won't respond to constant prompts. The most important lesson was restraint: no real-time state display (it prevents obsessive checking), no scores or streaks (they cause shame spirals), evening reflection only, all data on-device, no social features, and a pause mode for grief or overwhelm. Designing for time blindness means designing for vulnerability, and we took that seriously.