Precision Online Stopwatch and Lap Timer

A professional, high-performance web utility designed for tracking time intervals, measuring lap splits, and managing session data. Built for athletes, researchers, and productivity enthusiasts.

Core Features

• Millisecond Precision: Uses performance.now() for reliable, high-resolution timing.
• Lap & Split Recording: Record unlimited laps. Automatically calculates the duration of the current lap and the cumulative total time.
• Keyboard Shortcuts:
  • Space: Start / Stop
  • L: Record Lap
  • R: Reset
• Session Export: Export your complete lap history as a formatted CSV file for external analysis.
• Responsive Interface: Adaptive layout that works on smartphones, tablets, and desktop monitors.

UI/UX Specification

• Header: Minimalistic title with a clean description.
• Main Display: A large, high-contrast digital clock face showing HH:MM:SS.mmm.
• Control Panel: Three primary action buttons (Start/Stop, Lap, Reset) using high-visibility colors.
• Results Section: A clean table layout displaying Lap #, Split Time, and Total Time.
• Visual Feedback: Smooth CSS transitions for button states and list entry animations when a new lap is added.

Color Palette (Light Mode Only)

• Background: #ffffff
• Surface: #f8fafc (very light grey for panels)
• Primary Text: #1e293b (slate-800)
• Secondary Text: #64748b (slate-500)
• Primary Brand (Start/Stop): #2563eb (blue-600)
• Success (Lap): #16a34a (green-600)
• Danger (Reset): #dc2626 (red-600)

Technical Implementation Directives

1. Zero-Persistence Architecture:
   • All timing data must reside in standard JavaScript memory (Arrays/Objects).
   • Do NOT use localStorage, sessionStorage, or cookies to save state. If the page is refreshed, the session is cleared.
2. Performance:
   • Use requestAnimationFrame for smooth UI updates to ensure the clock is synced with the browser's refresh rate.
3. Formatting:
   • Ensure the UI handles window resizing gracefully. The digital clock font size should scale to fit the viewport width.
4. Iframe Compliance:
   • Avoid any browser-native blocking calls like alert() or confirm(). Use stylized HTML overlays if user interaction is required.
   • Ensure all links (if any) include target="_blank" and rel="noopener noreferrer".
5. Export Mechanism:
   • Dynamically generate the CSV data in memory using a Blob URL and trigger a hidden download link to allow the user to save their data.