Ever wished you could race against yesterday's you? Sprint Run turns your past runs into AI-powered virtual opponents. We call it Shadow Running — pick any previous run, and our AI reconstructs it as a real-time pacemaker that guides you with voice feedback 1. Run once to create your baseline 2. Choose a difficulty — Average You, Recent Best, or Personal Best 3. Start running. Your AI Shadow runs alongside you with real-time audio cues: "You're 3 seconds ahead" or "Shadow is pulling away"