:root {
  --bg: #000;
  --panel: #111;
  --panel-border: #2a2a2a;
  --text: #fff;
  --muted: #bdbdbd;
  --coin-size: min(72vw, 420px);
  --face-width: min(52vw, 260px);
  --radius: 20px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  background:
    radial-gradient(circle at top, #000000 0%, #000 55%);
  color: var(--text);
  font-family: system-ui, sans-serif;
}

.app {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
  width: min(100%, 720px);
  padding: 1.5rem 1rem 2rem;
}

.title {
  margin: 0;
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: 0.02em;
  text-align: center;
}

.coin-button {
  appearance: none;
  border: 0;
  background: transparent;
  padding: 0;
  cursor: pointer;
  border-radius: 999px;
  transition: transform 120ms ease;
}

.coin-button:hover {
  transform: scale(1.02);
}

.coin-button:active {
  transform: scale(0.98);
}

.coin-button:disabled {
  cursor: wait;
  opacity: 0.92;
}

.coin-button:focus-visible,
.secondary-button:focus-visible {
  outline: 3px solid #ffffff;
  outline-offset: 4px;
}

.coin {
  display: block;
  width: var(--coin-size);
  height: var(--coin-size);
  object-fit: contain;
}

.result-card {
  width: min(100%, 420px);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.9rem;
  padding: 1.25rem 1rem 1rem;
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  background: rgba(255, 255, 255, 0.06);
  backdrop-filter: blur(8px);
}

.result-heading {
  margin: 0;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.face {
  display: block;
  width: var(--face-width);
  height: auto;
  object-fit: contain;
}

.result {
  margin: 0;
  min-height: 1.5em;
  font-size: 1.1rem;
  font-weight: 600;
  text-align: center;
}

.secondary-button {
  appearance: none;
  border: 1px solid #3a3a3a;
  background: #1c1c1c;
  color: #fff;
  border-radius: 999px;
  padding: 0.75rem 1.1rem;
  font: inherit;
  cursor: pointer;
  transition: background 120ms ease, border-color 120ms ease, transform 120ms ease;
}

.secondary-button:hover {
  background: #262626;
  border-color: #4a4a4a;
}

.secondary-button:active {
  transform: translateY(1px);
}

.secondary-button:disabled {
  cursor: wait;
  opacity: 0.7;
}

/* --- smooth fade/scale when result updates --- */
.face,
.result {
  transition: opacity 180ms ease, transform 180ms ease;
}

.app.flipping .face,
.app.flipping .result {
  opacity: 0.5;
  transform: scale(0.98);
}

/* --- coin animation polish --- */
.coin {
  transition: transform 200ms ease;
}

.app.flipping .coin {
  transform: rotate(8deg) scale(1.02);
}

/* --- subtle entrance animation on load --- */
.app {
  animation: appFadeIn 300ms ease;
}

@keyframes appFadeIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* --- nicer button feedback --- */
.secondary-button,
.coin-button {
  -webkit-tap-highlight-color: transparent;
}

/* --- prevent text selection spam on mobile --- */
button, img {
  user-select: none;
  -webkit-user-drag: none;
}

/* --- 3D coin --- */

.coin-button {
  perspective: 1000px;
  width: var(--coin-size);
  height: var(--coin-size);
  padding: 0;
  display: grid;
  place-items: center;
}

.coin3d {
  width: 100%;
  height: 100%;
  position: relative;
  display: grid;
  place-items: center;
  transform-style: preserve-3d;
  transform-origin: center center;
  transition: transform 1.2s cubic-bezier(0.2, 0.7, 0.3, 1);
}

.coin-face {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  transform-origin: center center;
  border-radius: 50%;
}

/* front = heads */
.coin-face.front {
  transform: rotateY(0deg);
}

/* back = tails */
.coin-face.back {
  transform: rotateY(180deg);
}