/* ---- reset & base ---- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: #0d0d1a;
  font-family: 'Times New Roman', Times, serif;
  color: #a8c8ff;
  gap: 5rem;
}

/* ---- title ---- */
h4 {
  font-family: 'Times New Roman', Times, serif;
  font-size: 2rem;
  font-weight: normal;
  color: #a8c8ff;
  text-align: center;
  letter-spacing: 0.1em;
}

/* ---- 3D scene ---- */
.scene {
  perspective: 700px;
  width: 220px;
  height: 220px;
}

.cube {
  width: 220px;
  height: 220px;
  position: relative;
  transform-style: preserve-3d;
  transform: rotateX(0deg);
}

/* ---- cube faces ---- */
/*
  Slot layout (face CSS rotateX before cube rotation):
    Slot 0: face--front  →  rotateX(  0deg) translateZ(110px)
    Slot 1: face--top    →  rotateX( 90deg) translateZ(110px)
    Slot 2: face--back   →  rotateX(180deg) translateZ(110px)
    Slot 3: face--bottom →  rotateX(-90deg) translateZ(110px)

  Rotating cube by -90deg (increment) swings the top face (slot 1) to front.
  Rotating cube by +90deg (decrement) swings the bottom face (slot 3) to front.
*/

.face {
  position: absolute;
  width: 220px;
  height: 220px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 4rem;
  font-weight: bold;
  letter-spacing: -0.02em;
  border: 7px solid #a8c8ff;
  border-radius: 18px;
  background: rgba(10, 18, 48, 0.92);
  backface-visibility: hidden;
  color: #a8c8ff;
}

.face--front  { transform: rotateX(  0deg) translateZ(110px); }
.face--top    { transform: rotateX( 90deg) translateZ(110px); }
.face--back   { transform: rotateX(180deg) translateZ(110px); }
.face--bottom { transform: rotateX(-90deg) translateZ(110px); }

/* ---- controls ---- */
.controls {
  display: flex;
  gap: 2.5rem;
}

.controls button {
  width: 76px;
  height: 76px;
  font-size: 2.6rem;
  line-height: 1;
  border-radius: 50%;
  cursor: pointer;
  transition: filter 0.15s ease, transform 0.1s ease;
  user-select: none;
  -webkit-user-select: none;
}

.controls button:active {
  transform: scale(0.90);
}

#btn-increment {
  background: rgba(0, 70, 35, 0.80);
  border: 2px solid #3aff8a;
  color: #3aff8a;
}

#btn-increment:hover {
  filter: brightness(1.3);
}

#btn-decrement {
  background: rgba(80, 0, 20, 0.80);
  border: 2px solid #ff4466;
  color: #ff4466;
}

#btn-decrement:hover {
  filter: brightness(1.3);
}

/* ---- status line ---- */
#status {
  font-size: 0.8rem;
  opacity: 0.45;
  min-height: 1.3em;
  letter-spacing: 0.05em;
}