DragTree 应用
DragTree simulates a real NHRA Christmas Tree (drag strip starting lights) and uses your phone's accelerometer to measure reaction time to the millisecond — no tapping required.Mount your phone on the dash, stage up, watch the tree, and floor it. The app detects launch G-force automatically and records your RT. Fully offline — no internet, no account, no ads.
TREE MODES
• Pro Tree (.400s) — all three ambers fire simultaneously, green follows 0.400s later
• Sportsman Tree (.500s) — ambers count down one at a time, green follows 0.500s after the last amber
REACTION GRADING
• Perfect: 0–0.049s
• Pro: 0.050–0.099s
• Great: 0.100–0.199s
• Good: 0.200–0.349s
• Late: over 0.349s
• Red Light: launched before green
FEATURES
• Accelerometer launch detection — rolling baseline, no calibration step
• Three sensitivity presets: Gentle (0.15g), Normal (0.25g), Hard (0.46g) plus custom dial
• Session history — last 30 runs, personal best highlighted
• Reaction time trend chart — bar chart of recent runs
• Series mode — run 3, 5, or 10 back-to-back stages with avg RT, best/worst, and consistency score
• Optional audio cues — amber click, green chirp, result ping, red-light buzz
• Diagnostics screen — live G-force, sensor telemetry, last-launch breakdown
• Browser / simulator mode — on-screen FLOOR IT button for desktop practice
PERMISSIONS
• HIGH_SAMPLING_RATE_SENSORS — required for 125 Hz accelerometer sampling. No other sensor or location permissions used.
No internet connection required after install.
