style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.container {
  background: url(images/free.jpg) no-repeat center;
  background-size: cover;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  filter: brightness(50%);
}

.brightness-box {
  width: 400px;
  height: 60px;

  background: #f9f9f9;

  border-radius: 8px;

  padding: 0 20px;

  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brightness-box i {
  margin: 0 10px;
}

#range {
  cursor: pointer;
  width: 100%;
  height: 3px;

  background: #0a85ff;

  outline: none;
}

#range::-webkit-slider-thumb {
  -webkit-appearance: none;

  background: #333;

  width: 22px;
  height: 22px;

  border-radius: 50%;

  cursor: pointer;
}
#numberValue {
  border-left: 1px solid black;
  width: 35px;

  height: 35px;
  padding: 10px;

  text-align: center;
}