:root{
  --safe-top: env(safe-area-inset-top, 0px);
}

/* Back button */
.back-button{
  position: fixed;
  left: 22px;
  top: calc(var(--safe-top) + 28px);

  width: 48px;
  height: 48px;

  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0;

  padding: 0;
  margin: 0;

  border-radius: 999px;
  border: 2px solid var(--accent, #6c5ce7);
  border-color: var(--accent, #6c5ce7);

  background: #ffffff;

  box-shadow: 0 8px 22px rgba(0,0,0,.18);
  z-index: 99999;

  appearance: none;
  -webkit-appearance: none;
  cursor: pointer;
  outline: none;

  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
  user-select: none;
  touch-action: manipulation;

  transition:
    transform .10s ease,
    box-shadow .18s ease,
    border-color .18s ease;
}

.back-button:hover{
  border-color: var(--accent, #6c5ce7);   /* stays on chosen theme color */
  box-shadow: 0 10px 26px rgba(0,0,0,.22);
}

.back-button:active{
  transform: scale(.96);
  border-color: var(--accent, #6c5ce7);
}

.back-button:focus,
.back-button:focus-visible{
  outline: none !important;
  border-color: var(--accent, #6c5ce7);
  box-shadow:
    0 0 0 3px rgba(108,92,231,.14),
    0 8px 22px rgba(0,0,0,.18);
}

/* Filled triangle arrow */
.back-arrow{
  flex: 0 0 auto;
  width: 0;
  height: 0;

  border-top: 5px solid transparent;
  border-bottom: 5px solid transparent;
  border-right: 8px solid #1f2435;

  margin-right: -2px;

  transform: translateX(0);
  transition: transform .16s ease;
  will-change: transform;
}

/* Calendar icon */
.back-logo{
  flex: 0 0 auto;
  width: 25px;
  height: 25px;

  object-fit: contain;
  display: block;
  pointer-events: none;

  margin-left: -2px;
}

/* micro-interaction */
.back-button:hover .back-arrow,
.back-button:active .back-arrow,
.back-button.is-pressed .back-arrow{
  transform: translateX(-3px);
}

/* Small screens */
@media (max-width: 480px){
  .back-button{
    left: 18px;
    top: calc(var(--safe-top) + 22px);

    width: 44px;
    height: 44px;
  }

  .back-arrow{
    border-top-width: 4px;
    border-bottom-width: 4px;
    border-right-width: 7px;
  }

  .back-logo{
    width: 23px;
    height: 23px;
  }
}

/* Optional: kill focus ring glow on touch devices */
@media (hover: none) and (pointer: coarse){
  .back-button:focus,
  .back-button:focus-visible{
    border-color: var(--accent, #6c5ce7);
    box-shadow: 0 8px 22px rgba(0,0,0,.18) !important;
  }
}