style.css

/* Gece/gündüz modu  */

.switch {
  display: block;
  --width-of-switch: 3.5em;
  --height-of-switch: 2em;
  --size-of-icon: 1.4em;
  --slider-offset: 0.3em;
  width: var(--width-of-switch);
  height: var(--height-of-switch);
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 999;
}

.switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #f4f4f5;
  transition: 0.4s;
  border-radius: 30px;
}

.slider:before {
  position: absolute;
  content: "";
  height: var(--size-of-icon, 1.4em);
  width: var(--size-of-icon, 1.4em);
  border-radius: 20px;
  left: var(--slider-offset, 0.3em);
  top: 50%;
  transform: translateY(-50%);
  background: linear-gradient(40deg, #ff0080, #ff8c00 70%);
  transition: 0.4s;
}

input:checked + .slider {
  background-color: #303136;
}

input:checked + .slider:before {
  left: calc(100% - (var(--size-of-icon, 1.4em) + var(--slider-offset, 0.3em)));
  background: #303136;
  box-shadow: inset -3px -2px 5px -2px #8983f7, inset -10px -4px 0 0 #a3dafb;
}

/* Font */

body {
  font-family: "Inter", sans-serif;
}