Overlap
Kart pit-wall stopwatch for Android, with a vibrating approach alarm, post-session analysis and PDF export.
Timing a kart practice session with a physical stopwatch works for one driver. For two, it’s juggling: a hand on each button, a clipboard on your lap and no stats at the end of the day. Overlap is the pit-wall stopwatch I wanted: the drivers side by side on a phone, with the analysis ready when the session ends.
What it does
- Times two drivers at once on the free plan (the code already allows up to 20 on Pro), highlighting each driver’s best lap and the session best.
- Approach alarm: the phone vibrates in three steps as a driver gets close to the reference time (last lap, session best or a fixed time), so you look at the track at the right moment.
- After the session, it shows the ranking, a lap-by-lap chart, average, standard deviation and outlier laps, and compares two sessions side by side.
- Keeps each driver’s history: best lap per track, championship and session type, and how it evolves over time.
- Exports the session as PDF, CSV or a square image ready for WhatsApp and Instagram.
Decisions that mattered
One clock. Each driver has a Dart Stopwatch as the source of truth. Timers only redraw the screen and never accumulate time, so the limit on precision is your finger, not the software.
Vibration you can feel. On Samsung phones, Flutter’s HapticFeedback is toned down by the system until it’s barely there. The alarm drives the motor through the vibration package and counts how many steps it has fired on each lap, so each step vibrates once even though the screen updates dozens of times per second.
The out lap doesn’t skew the average. The first lap is usually much slower than the rest. If it’s over 1.5 times the median of the following laps, the analysis sets it aside on its own, and any lap can be included or excluded by hand.
Colors the paddock already knows. Purple for the session best, green for a personal best, orange for the approach. That’s F1’s visual vocabulary; inventing another one would only get in the way.
Where it stands
v1.0 runs on Android and is being prepared for Google Play. Next come a Pro mode with more drivers and reading lap times straight from timers like the AiM MyChron over Bluetooth.