Build a typing speed test

• A random passage is displayed and a text input (or key capture) accepts the typing; the timer starts on the first keystroke, not on page load
• Each character is highlighted as correct, incorrect or pending, and the current character is marked with a caret
• A countdown mode (for example 30 or 60 seconds) or a finish-on-completion mode ends the test and shows results
• WPM is computed as (correct characters / 5) / minutes elapsed, and accuracy as correct keystrokes over total keystrokes; live values are shown while typing
• Restart (button and Tab or Enter shortcut) selects a new random passage and resets everything, and the input keeps focus
• Backspace corrects mistakes; pasting is disabled, and the timer interval is cleaned up on finish and unmount

Only after every requirement works.

• Store personal bests and a history chart in localStorage
• Different passage lengths, punctuation and numbers modes
• Highlight problem keys after the test