/* ===== 开屏 ===== */
#scene-opening {
  background:
    radial-gradient(ellipse at 50% 15%, rgba(217, 164, 65, 0.12), transparent 55%),
    radial-gradient(ellipse at 80% 80%, rgba(143, 31, 31, 0.25), transparent 60%),
    var(--night);
  display: flex;
  align-items: center;
  justify-content: center;
}

.op-lines {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 18px;
  padding: 0 8vw;
  transition: opacity .8s ease;
}
.op-lines--gone { opacity: 0; pointer-events: none; }
.op-line {
  font-family: var(--font-kai);
  font-size: clamp(16px, 2.6vmin, 24px);
  letter-spacing: 3px;
  color: var(--gold-pale);
  text-align: center;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity .9s ease, transform .9s ease;
}
.op-line--show { opacity: 1; transform: translateY(0); }
.op-line:first-child { color: var(--gold); font-size: clamp(14px, 2.2vmin, 20px); }

.op-envelope {
  position: absolute;
  left: 50%;
  top: 50%;
  width: clamp(90px, 16vmin, 150px);
  transform: translate(-50%, -50%) scale(.3);
  opacity: 0;
  transition: opacity .9s ease, transform .9s cubic-bezier(.2, 1.4, .4, 1);
}
.op-envelope svg { width: 100%; height: auto; filter: drop-shadow(0 6px 18px rgba(217, 164, 65, .35)); }
.op-envelope--show { opacity: 1; transform: translate(-50%, -50%) scale(1); }
.op-envelope--gone { opacity: 0; transform: translate(-50%, -120%) scale(.6); pointer-events: none; }

.op-letter {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 6vh 5vw 20vh;
  opacity: 0;
  transform: translateY(30px);
  transition: opacity .9s ease, transform .9s ease;
  pointer-events: none;
}
.op-letter--show { opacity: 1; transform: translateY(0); pointer-events: auto; }
.op-letter__paper {
  width: min(92vw, 660px);
  max-height: 66vh;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  background:
    repeating-linear-gradient(0deg, rgba(43, 35, 32, 0.03) 0 1px, transparent 1px 3px),
    linear-gradient(180deg, var(--paper), var(--paper-dark));
  border: 2px solid var(--gold);
  border-radius: 8px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, .5), inset 0 0 40px rgba(217, 164, 65, .12);
  padding: 26px 26px 20px;
}
.op-letter__title {
  font-family: var(--font-kai);
  font-size: clamp(15px, 2.3vmin, 19px);
  color: var(--red-deep);
  text-align: center;
  margin-bottom: 16px;
  line-height: 1.7;
}
.op-letter__para {
  font-family: var(--font-kai);
  font-size: clamp(15px, 2.4vmin, 20px);
  line-height: 2.05;
  color: var(--ink);
  margin-bottom: 12px;
  text-align: justify;
}
.op-ch { opacity: 0; transition: opacity .35s ease; }
.op-ch--on, .op-letter--all .op-ch { opacity: 1; }
.op-letter__signer {
  font-family: var(--font-kai);
  text-align: right;
  color: var(--red-deep);
  font-size: clamp(15px, 2.4vmin, 20px);
  opacity: 0;
  transition: opacity 1s ease;
}
.op-letter--signed .op-letter__signer { opacity: 1; }

.op-footer {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 4vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 0 6vw;
  opacity: 0;
  transform: translateY(14px);
  transition: opacity .9s ease, transform .9s ease;
  pointer-events: none;
}
.op-footer--show { opacity: 1; transform: translateY(0); pointer-events: auto; }
.op-caption {
  font-family: var(--font-kai);
  color: var(--gold-pale);
  font-size: clamp(14px, 2.2vmin, 18px);
  text-align: center;
}

.op-skip {
  position: absolute;
  top: 14px;
  right: 14px;
  z-index: 5;
  opacity: .8;
}

/* ===== 第一幕·启程 ===== */
#scene-act1 {
  background:
    radial-gradient(ellipse at 50% 62%, rgba(224, 80, 56, 0.30), transparent 62%),
    linear-gradient(180deg, #3c0d0d 0%, var(--red-deep) 55%, #5a1414 100%);
  display: flex;
  align-items: center;
  justify-content: center;
}
.a1-bg {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  opacity: .28;
  pointer-events: none;
}
.a1-bg svg { display: block; width: 100%; height: auto; }

.a1-lines {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
  padding: 0 7vw 12vh;
  max-width: 860px;
}
.a1-line {
  font-family: var(--font-kai);
  font-size: clamp(15px, 2.6vmin, 23px);
  letter-spacing: 2px;
  line-height: 1.8;
  color: var(--gold-pale);
  text-align: center;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity .9s ease, transform .9s ease;
}
.a1-line--show { opacity: 1; transform: translateY(0); }
.a1-tip {
  font-size: clamp(12px, 2vmin, 16px);
  color: var(--gold);
  border-top: 1px dashed rgba(217, 164, 65, .5);
  padding-top: 12px;
  margin-top: 6px;
}

.a1-enter {
  position: absolute;
  left: 50%;
  bottom: 5vh;
  transform: translateX(-50%) translateY(14px);
  opacity: 0;
  transition: opacity .8s ease, transform .8s ease;
  pointer-events: none;
  z-index: 2;
}
.a1-enter--show { opacity: 1; transform: translateX(-50%) translateY(0); pointer-events: auto; }