Zoned is a free, open-source app that builds running plans and workouts around your own heart-rate or pace zones. No account, no backend, no paywall, everything runs locally in your browser, offline included. Inside: 256 structured workouts, 9 plans from 5K to marathon, a real-world route generator, a race-day pacing simulator and 12 calculators. Export to Garmin FIT, Strava, GPX, calendar or PDF. MIT licensed, self-host it or contribute a session.