:root{
  --bg:#090c14;
  --panel:rgba(17,23,35,.86);
  --panel2:rgba(24,32,48,.78);
  --text:#f4f7fb;
  --muted:#aeb8c8;
  --line:rgba(255,255,255,.12);
  --line-strong:rgba(103,232,146,.30);
  --accent:#74c7ff;
  --accent-soft:rgba(103,232,146,.10);
  --accent2:#9b8cff;
  --danger:#ff7f8c;
  --gold:#f1d58a;
  --white-key:#f6f1e7;
  --white-key-edge:#c9c4ba;
  --black-key:#111318;
  --black-key-edge:#2c3038;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI","Noto Sans JP",sans-serif}
body{min-height:100vh;overflow-x:hidden}
button,input,textarea{font:inherit}
button{cursor:pointer}
button:focus-visible,input:focus-visible,textarea:focus-visible{outline:3px solid rgba(116,199,255,.6);outline-offset:2px}

.stage{
  position:relative;
  min-height:100vh;
  padding:28px 18px 18px;
  background:
    radial-gradient(circle at 20% 10%,rgba(116,199,255,.11),transparent 30%),
    radial-gradient(circle at 80% 18%,rgba(155,140,255,.11),transparent 28%),
    linear-gradient(180deg,#0b1020 0%,#090c14 55%,#07090f 100%);
}
.decor{position:absolute;inset:0;pointer-events:none;overflow:hidden}
.staff{
  position:absolute;left:-4%;right:-4%;top:126px;height:82px;opacity:.20;
  transform:rotate(-1.5deg);
  background:repeating-linear-gradient(to bottom,transparent 0 12px,rgba(175,214,255,.68) 13px 14px);
  filter:drop-shadow(0 0 8px rgba(116,199,255,.18));
}
.beam{
  position:absolute;top:-80px;width:260px;height:560px;opacity:.20;
  background:linear-gradient(180deg,rgba(116,199,255,.36),rgba(116,199,255,.06) 55%,transparent);
  filter:blur(18px);transform-origin:top center;
}
.beam.b1{left:8%;transform:rotate(13deg)}
.beam.b2{right:8%;transform:rotate(-13deg);background:linear-gradient(180deg,rgba(155,140,255,.32),rgba(155,140,255,.05) 55%,transparent)}
.note{
  position:absolute;color:rgba(210,232,255,.34);font-size:30px;
  text-shadow:0 0 12px rgba(116,199,255,.22);
  animation:floatNote 16s ease-in-out infinite;
}
.note.n1{left:7%;top:22%;animation-delay:-2s}.note.n2{left:24%;top:11%;animation-delay:-8s}
.note.n3{right:17%;top:20%;animation-delay:-5s}.note.n4{right:5%;top:36%;animation-delay:-11s}
.note.n5{left:12%;top:62%;animation-delay:-13s}.note.n6{right:22%;top:67%;animation-delay:-3s}
.spark{
  position:absolute;width:5px;height:5px;border-radius:50%;
  background:rgba(224,241,255,.65);box-shadow:0 0 14px rgba(116,199,255,.65);
  animation:twinkle 4.5s ease-in-out infinite;
}
.spark.s1{left:17%;top:31%;animation-delay:-1s}.spark.s2{left:37%;top:17%;animation-delay:-3s}
.spark.s3{right:34%;top:29%;animation-delay:-2s}.spark.s4{right:12%;top:14%;animation-delay:-4s}
.spark.s5{left:8%;top:53%;animation-delay:-2.5s}.spark.s6{right:19%;top:58%;animation-delay:-1.5s}
@keyframes floatNote{0%,100%{transform:translateY(16px) rotate(-5deg);opacity:.18}50%{transform:translateY(-22px) rotate(5deg);opacity:.48}}
@keyframes twinkle{0%,100%{transform:scale(.65);opacity:.25}50%{transform:scale(1.35);opacity:.85}}

.app{position:relative;z-index:1;max-width:1180px;margin:0 auto}
.topbar{display:flex;justify-content:space-between;gap:16px;align-items:flex-start;flex-wrap:wrap}
.brand{position:relative;padding:4px 0 8px}
.brand h1{
  position:relative;margin:0;display:inline-block;
  font-family:Georgia,"Times New Roman",serif;
  font-size:clamp(2.2rem,5.5vw,5rem);font-weight:700;letter-spacing:.11em;
  color:#f7fbff;
  text-shadow:0 2px 0 rgba(0,0,0,.25),0 0 24px rgba(116,199,255,.16);
}
.brand h1::before{
  content:"♪";display:inline-block;margin-right:.24em;color:var(--gold);
  font-size:.66em;vertical-align:.18em;text-shadow:0 0 14px rgba(241,213,138,.28);
}
.brand h1::after{
  content:"";position:absolute;left:1.06em;right:.03em;bottom:-7px;height:5px;border-radius:99px;
  background:repeating-linear-gradient(90deg,#f5f1e8 0 24px,#14171d 24px 31px,#f5f1e8 31px 55px);
  opacity:.82;box-shadow:0 2px 10px rgba(0,0,0,.32);
}
.brand .subtitle{margin:.72rem 0 0 1.1em;color:#d9e2ef;font-size:clamp(1rem,2vw,1.35rem);letter-spacing:.04em}
.lang-switch{display:inline-flex;background:rgba(255,255,255,.06);border:1px solid var(--line);border-radius:999px;padding:4px}
.lang-switch button{border:0;background:transparent;color:var(--muted);padding:9px 14px;border-radius:999px}
.lang-switch button.active{background:linear-gradient(135deg,rgba(116,199,255,.25),rgba(155,140,255,.25));color:var(--text)}
.tagline{margin:24px 0 8px;font-size:clamp(1.05rem,2.1vw,1.5rem);font-weight:700}
.description{margin:0 0 22px;color:var(--muted);line-height:1.8;max-width:900px}
.examples{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:22px}
.chip{padding:7px 11px;border:1px solid var(--line);border-radius:999px;background:rgba(255,255,255,.04);color:#dbe7f5;font-size:.9rem}

.panel{background:var(--panel);border:1px solid var(--line);border-radius:22px;padding:18px;backdrop-filter:blur(12px);box-shadow:0 20px 70px rgba(0,0,0,.25)}
.piano-section{margin-top:8px}
.section-title{display:flex;align-items:center;justify-content:space-between;gap:14px;margin-bottom:12px}
.section-title h2{margin:0;font-size:1rem;letter-spacing:.08em;color:#dfe8f4}
.keyboard-wrap{position:relative;width:100%;padding-top:10px}
.keyboard{
  position:relative;
  width:100%;
  height:clamp(210px,29vw,310px);
  user-select:none;
  touch-action:none;
}
.white-keys{position:absolute;inset:0;display:flex}
.key.white{
  position:relative;flex:1;border:1px solid var(--white-key-edge);border-radius:0 0 9px 9px;
  background:linear-gradient(180deg,#fffdfa 0%,var(--white-key) 82%,#e5ded1 100%);
  box-shadow:inset 0 -8px 0 rgba(0,0,0,.05);
}
.key.white + .key.white{border-left-width:0}
.key-label{position:absolute;bottom:10px;left:50%;transform:translateX(-50%);text-align:center;color:#1c2330;font-weight:700;line-height:1.15;font-size:clamp(.55rem,1.3vw,.9rem);pointer-events:none}
.key-label .kana{display:block;font-size:.85em;margin-bottom:2px;color:#505765}
.black-key{
  position:absolute;top:0;height:62%;width:4.8%;
  transform:translateX(-50%);
  z-index:3;border-radius:0 0 7px 7px;border:1px solid var(--black-key-edge);
  background:linear-gradient(180deg,#242831 0%,var(--black-key) 78%,#050607 100%);
  box-shadow:0 7px 10px rgba(0,0,0,.45);
}
.black-label{position:absolute;bottom:10px;left:50%;transform:translateX(-50%) rotate(-90deg);color:#dbe4ef;font-size:clamp(.48rem,1vw,.72rem);white-space:nowrap;pointer-events:none}
.key.active{
  background:linear-gradient(180deg,#dff5ff 0%,#9edbff 70%,#78c5ff 100%);
  box-shadow:0 0 22px rgba(116,199,255,.7),inset 0 -7px 0 rgba(0,0,0,.08);
}
.black-key.active{
  background:linear-gradient(180deg,#9cdaff 0%,#4aa9e8 72%,#277aaf 100%);
  box-shadow:0 0 20px rgba(116,199,255,.85);
}

.status-strip{display:flex;gap:18px;flex-wrap:wrap;margin-top:14px;color:#dbe6f3}
.status-item{background:rgba(255,255,255,.045);border:1px solid var(--line);padding:9px 12px;border-radius:12px;min-width:150px}
.status-item strong{display:block;font-size:.8rem;color:var(--muted);margin-bottom:3px}

.controls{margin-top:18px;display:grid;gap:16px}
.field-label{display:block;margin-bottom:7px;font-weight:700}
textarea{
  width:100%;min-height:108px;resize:vertical;border-radius:14px;border:1px solid var(--line);
  background:rgba(8,12,20,.75);color:var(--text);padding:14px 15px;font-size:16px;line-height:1.55
}
.segmented{display:inline-flex;border:1px solid var(--line);border-radius:12px;overflow:hidden;background:rgba(255,255,255,.04)}
.segmented button{border:0;border-right:1px solid var(--line);background:transparent;color:var(--muted);padding:10px 14px}
.segmented button:last-child{border-right:0}.segmented button.active{background:rgba(116,199,255,.16);color:var(--text)}
.button-row{display:flex;gap:10px;flex-wrap:wrap}
.action{border:1px solid var(--line);border-radius:12px;padding:11px 15px;background:rgba(255,255,255,.06);color:var(--text);min-height:44px}
.action.primary{background:linear-gradient(135deg,rgba(116,199,255,.28),rgba(155,140,255,.25));border-color:rgba(116,199,255,.35)}
.action.danger{color:#ffd8dd}
.action:disabled{opacity:.45;cursor:not-allowed}
.knobs{display:grid;grid-template-columns:minmax(180px,1fr) minmax(220px,1.3fr);gap:16px}
.control-card{background:var(--panel2);border:1px solid var(--line);border-radius:14px;padding:13px}
.control-card label{display:flex;justify-content:space-between;gap:12px;align-items:center;color:#dfe8f4;margin-bottom:8px}
input[type="number"]{width:90px;background:#0b101b;color:var(--text);border:1px solid var(--line);border-radius:9px;padding:8px}
input[type="range"]{width:100%}
.message{min-height:24px;color:#ffd4da;font-size:.93rem}

.back-link{
  display:inline-flex;
  align-items:center;
  gap:8px;
  min-height:44px;
  padding:9px 14px;
  border:1px solid var(--line);
  border-radius:12px;
  color:var(--text);
  background:rgba(255,255,255,.025);
  text-decoration:none;
  font-size:.88rem;
  font-weight:750;
  white-space:nowrap;
}
.back-link:hover,.back-link:focus-visible{
  border-color:var(--line-strong);
  background:var(--accent-soft);
  outline:none;
}

footer{margin:22px 0 0;text-align:center;color:#97a3b5;font-size:.9rem}
footer a{color:#b8dfff;text-underline-offset:3px}

.rotate-overlay{
  display:none;position:absolute;inset:0;z-index:20;background:rgba(5,8,14,.96);
  align-items:center;justify-content:center;text-align:center;padding:28px;border-radius:22px
}
.rotate-card{max-width:420px}.rotate-icon{font-size:3rem;margin-bottom:10px}.rotate-card h3{font-size:1.5rem;margin:.2rem 0 .5rem}.rotate-card p{color:var(--muted);line-height:1.7}

@media(max-width:720px) and (orientation:portrait){
  .piano-section{position:relative}
  .piano-section .rotate-overlay{display:flex}
}
@media(max-width:820px){
  .stage{padding:18px 10px 14px}
  .panel{padding:12px;border-radius:16px}
  .knobs{grid-template-columns:1fr}
  .decor .note:nth-child(n+4),.decor .spark:nth-of-type(n+8){display:none}
  .beam{opacity:.11}
  .staff{opacity:.13}
  .back-link{width:100%;justify-content:center}
  .keyboard{height:220px}
}
@media(prefers-reduced-motion:reduce){
  *,*::before,*::after{animation:none!important;scroll-behavior:auto!important;transition:none!important}
}