style.css

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f0f0;
  }

#background {
  height: 100%;
  width: 100%;
  position: fixed;
  background-color: greenyellow;
  background-image: url("https://i0.wp.com/www.kridha.net/wp-content/uploads/2021/01/Landscape-Vector-Illustration-Background.jpg?fit=960%2C540&ssl=1");
  background-repeat: no-repeat;
  background-size: cover;
  opacity: 0.7;
  display: flex;
  justify-content: center;
  align-items: center;
}

.stopwatch {
    text-align: center;
    background: #fff;
    width: 25rem;
    padding: 20px;
    border-radius: 10px;
}
#timer {
    font-size: 3rem;
    margin-bottom: 20px;
}
#laps {
    height: 100px;
    max-height: 150px;
    overflow-y: auto;
    border-top: 1px solid #ddd;
    padding-top: 10px;
    margin-bottom: 10px;
}


.buttons button {
    font-size: 1.2rem;
    padding: 10px 20px;
    margin: 5px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}
#startStop {
    background: #4CAF50;
    color: #fff;
}
#lapReset {
    background: #f44336;
    color: #fff;
}
button:disabled {
    background: #ccc;
    cursor: not-allowed;
}