Please fork this repo and do the missions.

Your missions:

• Fix: score counting
• Fix: UI layout should not shift when start button disappears
• Fix: game timer should stop at zero and game should end
• Fix: game timer should not show when game is not playing
• Fix: user should not be able to click the same mole many times
• Fix: setTimeout() memory leak

• Feat: clicking on empty squares = lose 5 points. score should not go below zero
• Feat: show highest score
• Feat: add Hard Mode. player can select Easy / Hard modes (no need high score for Hard Mode)

Easy Mode (default) - game duration is 30 seconds and -5 points if wrong click
Hard Mode - game duration is 1 minute and timer is 0 instantly if wrong click