* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #0d5c2e 0%, #1a7d3e 30%, #228b45 50%, #1a7d3e 70%, #0d5c2e 100%);
  color: #f5f5dc;
  font-family: 'Georgia', 'Times New Roman', serif;
  overflow: hidden;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image: radial-gradient(circle at 20% 30%, rgba(255, 215, 0, 0.08) 0%, transparent 40%),
    radial-gradient(circle at 80% 70%, rgba(255, 215, 0, 0.06) 0%, transparent 40%);
  pointer-events: none;
}

h1 {
  margin-bottom: 2rem;
}

#envelope {
  position: relative;
  cursor: pointer;
  width: 80vmin;
  max-width: 500px;
  perspective: 1000px;
  margin: 0;
  padding: 0;
  border: none;
  background: none;
  font: inherit;
  color: inherit;
}

.envelope {
  position: relative;
  width: 100%;
  aspect-ratio: 3 / 2;
}

.envelope-flyaway {
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, #2d7a4a, #228b45);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
  border: 2px solid #1a5c34;
}

.envelope-body {
  position: absolute;
  inset: 0;
  z-index: 1;
  background: linear-gradient(to bottom, #2d7a4a, #3d9a5c 20%);
  border: 2px solid #1a5c34;
  transition: z-index 0s 0.6s;
}

.envelope-top-flap {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 60%;
  background: linear-gradient(160deg, #228b45 0%, #2d9a52 50%, #1a6b38 100%);
  z-index: 3;
  clip-path: polygon(0 0, 100% 0, 50% 100%);
  transform-origin: top;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1), z-index 0s 0.2s;
  filter: drop-shadow(0 2px 4px rgba(0,0,0,0.2));
  border: 2px solid #1a5c34;
}

.letter {
  position: absolute;
  bottom: 10%;
  left: 5%;
  width: 90%;
  height: 80%;
  background: linear-gradient(to bottom, #f8fff8 0%, #e8f5e9 100%);
  color: #1b5e20;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  z-index: 0;
  transition: transform 0.6s ease;
  box-shadow: 0 0 10px rgba(0,0,0,0.15), inset 0 0 0 3px #c8e6c9;
  border: 2px solid #2e7d32;
}

.letter-decoration {
  position: absolute;
  font-size: 1.5rem;
  opacity: 0.7;
}

.letter-decoration--top {
  top: 0.5rem;
  left: 50%;
  transform: translateX(-50%);
}

.letter-decoration--bottom {
  bottom: 0.5rem;
  left: 50%;
  transform: translateX(-50%);
}

.letter-message {
  margin: 0;
  font-size: clamp(1rem, 4vw, 1.5rem);
  font-weight: 600;
  text-align: center;
  padding: 0 1rem;
  text-shadow: 0 0 20px rgba(255, 215, 0, 0.3);
  color: #1b5e20;
}

.letter-accent {
  position: absolute;
  bottom: 0.75rem;
  right: 1rem;
  font-size: 1.25rem;
  opacity: 0.8;
}


#envelope:not(.open):hover .envelope-top-flap {
  transform: rotateX(180deg);
  z-index: 0;
  transition: transform 0.6s ease, z-index 0s 0.15s;
}

#envelope:not(.open):hover .letter {
  transform: translateY(-30%);
  z-index: 1;
  transition: transform 0.6s ease, z-index 0s 0.15s;
}

#envelope:not(.open):hover .envelope-body {
  z-index: 2;
  transition: z-index 0s 0.15s;
}

#envelope.open .envelope-top-flap {
  transform: rotateX(180deg);
  z-index: 0;
  transition: transform 0.3s ease;
}

#envelope.open .envelope-flyaway {
  transition: transform 0.8s cubic-bezier(0.4, 0, 0.2, 1);
  transform: translateY(100vh);
}

#envelope.open .letter {
  position: fixed;
  left: 50%;
  top: 50%;
  width: 90%;
  max-width: 420px;
  height: auto;
  min-height: 200px;
  margin: 0;
  z-index: 100;
  transform: translate(-50%, -50%);
  transition: none;
  animation: letterFocus 0.8s cubic-bezier(0.4, 0, 0.2, 1) forwards;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4), 0 0 0 4px #ffd700;
  border-color: #b8860b;
}

@keyframes letterFocus {
  from {
    transform: translate(-50%, -50%) scale(0.5);
    opacity: 0.9;
  }
  to {
    transform: translate(-50%, -50%) scale(1.15);
    opacity: 1;
  }
}

.letter-actions {
  position: fixed;
  left: 50%;
  top: 58%;
  transform: translateX(-50%);
  display: flex;
  gap: 1.25rem;
  justify-content: space-between;
  min-width: 260px;
  width: max-content;
  z-index: 101;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease 0.85s;
}

#envelope.open ~ .letter-actions {
  opacity: 1;
  pointer-events: auto;
}

.letter-btn {
  padding: 0.6rem 1.5rem;
  font-size: 1.1rem;
  font-weight: 600;
  font-family: Georgia, 'Times New Roman', serif;
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  border: 2px solid;
}

.letter-btn--yes {
  background: linear-gradient(to bottom, #2e7d32, #1b5e20);
  color: #f8fff8;
  border-color: #1b5e20;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.letter-btn--yes:hover {
  transform: scale(1.05);
  box-shadow: 0 0 0 3px #ffd700, 0 6px 16px rgba(0, 0, 0, 0.25);
}

.letter-btn--no {
  background: linear-gradient(to bottom, #f8fff8, #e8f5e9);
  color: #1b5e20;
  border-color: #2e7d32;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.letter-btn--no:hover {
  transform: scale(1.02);
  box-shadow: 0 0 0 2px #2e7d32, 0 6px 16px rgba(0, 0, 0, 0.15);
}

#envelope.open ~ .hint {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease;
}

body.letter-open h1 {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease;
}

.yippee-popup {
  position: fixed;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%) scale(0);
  z-index: 200;
  font-size: clamp(2rem, 8vw, 4rem);
  font-weight: 800;
  color: #ffd700;
  text-shadow: 0 0 20px rgba(255, 215, 0, 0.6), 0 2px 4px rgba(0, 0, 0, 0.3);
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.2s ease;
}

.yippee-popup.yippee-popup--show {
  opacity: 1;
  animation: yippeePop 0.5s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}

@keyframes yippeePop {
  from {
    transform: translate(-50%, -50%) scale(0);
  }
  70% {
    transform: translate(-50%, -50%) scale(1.2);
  }
  to {
    transform: translate(-50%, -50%) scale(1);
  }
}

.hint {
  margin-top: 2rem;
  font-size: 0.9rem;
  letter-spacing: 2px;
  opacity: 0.6;
  color: #c8e6c9;
  text-shadow: 0 0 8px rgba(0,0,0,0.3);
}