/* Study Together V4 — mobile-first styles matching the reference mockups */
:root{
  --blue:#2563eb;--blue2:#1d4ed8;--blue-soft:#eef4ff;--ink:#0f172a;--ink2:#334155;--muted:#64748b;--line:#e6eaf2;
  --bg:#f5f7fb;--card:#fff;--green:#16a34a;--green-soft:#dcfce7;--red:#ef4444;--amber:#b45309;--amber-soft:#fef3c7;
  --shadow:0 1px 2px rgba(15,23,42,.04),0 6px 20px rgba(15,23,42,.06);--r:16px;
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;background:var(--bg)}
body{font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;color:var(--ink);font-size:15px;line-height:1.45}
button,input,select,textarea{font:inherit;color:inherit}
button{cursor:pointer;border:0;background:none;padding:0}
a{color:inherit}
.ic{display:block;flex:none}
.app{max-width:520px;margin:0 auto;min-height:100vh;min-height:100dvh;background:var(--bg);position:relative}
.page{padding:16px 16px 96px}
.muted{color:var(--muted)}.small{font-size:13px}.tiny{font-size:12px}
.row{display:flex;align-items:center;gap:10px}.between{justify-content:space-between}.wrap{flex-wrap:wrap}
.grow{flex:1;min-width:0}
.hr{border:0;border-top:1px solid var(--line);margin:16px 0}
.hidden{display:none!important}

/* top bar */
.topbar{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.96);backdrop-filter:blur(8px);border-bottom:1px solid var(--line);padding:10px 16px;padding-top:calc(10px + env(safe-area-inset-top));display:flex;align-items:center;gap:10px}
.topbar .brand{font-weight:800;font-size:18px;letter-spacing:-.3px;flex:1}
.topbar .brand span{color:var(--blue)}
.iconbtn{width:40px;height:40px;border-radius:12px;display:grid;place-items:center;color:var(--ink2);position:relative}
.iconbtn:active{background:#f1f5f9}
.dot{position:absolute;top:8px;right:9px;width:8px;height:8px;border-radius:50%;background:var(--red);border:2px solid #fff}
.pagehead{display:flex;align-items:center;gap:8px;margin:-4px 0 14px}
.pagehead h1{font-size:18px;margin:0;flex:1;text-align:center;padding-right:40px}
.pagehead.left h1{text-align:left;padding:0}

/* avatars */
.av{border-radius:50%;display:grid;place-items:center;color:#fff;font-weight:800;flex:none;position:relative}
.av.s28{width:28px;height:28px;font-size:11px}.av.s40{width:40px;height:40px;font-size:15px}.av.s48{width:48px;height:48px;font-size:17px}
.av.s72{width:72px;height:72px;font-size:24px}.av.s96{width:96px;height:96px;font-size:32px}.av.s116{width:116px;height:116px;font-size:38px}

/* cards & sections */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:16px;box-shadow:var(--shadow)}
.stack{display:grid;gap:12px}
.sec{display:flex;align-items:center;justify-content:space-between;margin:22px 0 10px}
.sec h2{font-size:16px;margin:0}
.link{color:var(--blue);font-weight:600;font-size:13px}
.hello{margin:4px 0 14px}.hello b{font-size:20px;display:block;letter-spacing:-.3px}

/* session card */
.scard{cursor:pointer}
.scard .t{font-weight:700;font-size:15px}
.scard .t em{font-style:normal;color:var(--blue)}
.scard .line{display:flex;align-items:center;gap:6px;color:var(--muted);font-size:13px;margin-top:6px}
.badge{font-size:11px;font-weight:700;padding:3px 9px;border-radius:999px;white-space:nowrap}
.badge.green{background:var(--green-soft);color:#166534}.badge.amber{background:var(--amber-soft);color:var(--amber)}
.badge.gray{background:#f1f5f9;color:#475569}.badge.live{background:#dcfce7;color:#15803d}
.badge.live::before{content:"";display:inline-block;width:6px;height:6px;border-radius:50%;background:#22c55e;margin-right:5px;vertical-align:1px}
.tag{display:inline-block;font-size:12px;padding:4px 10px;border-radius:999px;background:var(--blue-soft);color:var(--blue2);font-weight:600}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:7px;border-radius:12px;padding:11px 16px;font-weight:700;font-size:15px;text-decoration:none;white-space:nowrap}
.btn.sm{padding:7px 16px;font-size:13px;border-radius:10px}
.btn.primary{background:var(--blue);color:#fff}.btn.primary:active{background:var(--blue2)}
.btn.soft{background:var(--blue-soft);color:var(--blue)}
.btn.ghost{background:#f1f5f9;color:var(--ink2)}
.btn.outline{background:#fff;border:1px solid var(--line);color:var(--ink2)}
.btn.danger{background:#fee2e2;color:#b91c1c}
.btn.wa{background:#e9fbef;color:#128c4a}
.btn.block{width:100%}.btn.big{padding:15px 18px;font-size:16px;border-radius:14px}
.btn:disabled{opacity:.6}
.actions{display:flex;gap:8px;flex-wrap:wrap}

/* forms */
.form{display:grid;gap:14px}
.field label{display:block;font-size:13px;color:var(--ink2);margin-bottom:6px;font-weight:600}
.field input,.field select,.field textarea,.search input{width:100%;padding:12px 13px;border:1px solid var(--line);border-radius:12px;background:#fff;font-size:16px;outline:none}
.field input:focus,.field select:focus,.field textarea:focus,.search input:focus{border-color:#93b4fb;box-shadow:0 0 0 3px #dbe7ff}
.two{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px}
.two>*{min-width:0}
.field input[type=date],.field input[type=time]{min-width:0;-webkit-appearance:none;appearance:none;min-height:46px}
.hint{font-size:12px;color:var(--muted);margin-top:5px}
.toggle{display:flex;align-items:center;justify-content:space-between;gap:12px}
.switch{position:relative;width:50px;height:30px;flex:none}
.switch input{opacity:0;width:0;height:0}
.switch span{position:absolute;inset:0;background:#cbd5e1;border-radius:30px;transition:.2s}
.switch span::after{content:"";position:absolute;width:24px;height:24px;left:3px;top:3px;background:#fff;border-radius:50%;transition:.2s;box-shadow:0 1px 3px rgba(0,0,0,.2)}
.switch input:checked+span{background:#22c55e}.switch input:checked+span::after{transform:translateX(20px)}
.chips{display:flex;gap:8px;flex-wrap:wrap}
.chip{padding:8px 13px;border-radius:999px;background:#fff;border:1px solid var(--line);color:var(--ink2);font-size:13px;font-weight:600}
.chip.on{background:var(--blue-soft);border-color:#bcd0fb;color:var(--blue2)}
.search{margin-bottom:12px;position:relative}
.search input{padding-left:40px}
.search .ic{position:absolute;left:12px;top:13px;color:var(--muted)}

/* subject tiles */
.tiles{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
.tile{background:#fff;border:1px solid var(--line);border-radius:14px;padding:14px 6px 12px;text-align:center;font-size:12px;font-weight:600;color:var(--ink2);display:flex;flex-direction:column;align-items:center;gap:8px}
.tile .ti{width:44px;height:44px;border-radius:12px;display:grid;place-items:center;font-size:22px}
.subjicon{width:52px;height:52px;border-radius:14px;display:grid;place-items:center;font-size:26px;flex:none}

/* how it works */
.steps{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}
.step{background:#fff;border:1px solid var(--line);border-radius:14px;padding:12px}
.step b{display:flex;align-items:center;gap:8px;font-size:14px}
.step b i{font-style:normal;width:22px;height:22px;border-radius:50%;background:var(--blue);color:#fff;display:grid;place-items:center;font-size:12px}
.step p{margin:6px 0 0;font-size:12px;color:var(--muted)}

/* detail */
.stats{display:grid;grid-template-columns:repeat(3,1fr);border:1px solid var(--line);border-radius:14px;margin:14px 0}
.stats>div{padding:12px 6px;text-align:center;font-size:12px;color:var(--muted)}
.stats>div+div{border-left:1px solid var(--line)}
.stats b{display:block;color:var(--ink);font-size:14px;margin-top:4px}
.stats .si{font-size:18px}
.notice{padding:11px 13px;border-radius:12px;background:var(--blue-soft);color:#1e40af;font-size:13px}
.notice.ok{background:#ecfdf5;color:#166534}.notice.wait{background:#fffbeb;color:#92400e}.notice.off{background:#f1f5f9;color:#475569}
.joinbar{display:flex;gap:10px;margin-top:16px}
.savebtn{width:52px;height:52px;border-radius:14px;border:1px solid var(--line);display:grid;place-items:center;color:var(--ink2);background:#fff;flex:none}
.savebtn.on{color:var(--blue);background:var(--blue-soft);border-color:#bcd0fb}
.savebtn.on svg{fill:currentColor}

/* bottom nav */
.nav{position:fixed;bottom:0;left:0;right:0;z-index:30;background:#fff;border-top:1px solid var(--line);padding-bottom:env(safe-area-inset-bottom)}
.nav-inner{max-width:520px;margin:auto;display:grid;grid-template-columns:repeat(4,1fr);height:64px}
.nav button{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:3px;color:#94a3b8;font-size:11px;font-weight:600}
.nav button.active{color:var(--blue)}

/* welcome / onboarding */
.welcome{min-height:100vh;min-height:100dvh;display:flex;flex-direction:column;background:linear-gradient(180deg,#eaf2ff 0%,#fff 55%);padding:24px 22px calc(28px + env(safe-area-inset-bottom))}
.illus{position:relative;height:300px;margin:10px auto 0;width:100%;max-width:340px}
.illus .blob{position:absolute;inset:30px 10px 10px;border-radius:50%;background:radial-gradient(circle at 50% 40%,#dbe8ff,#eef4ff 60%,transparent 70%)}
.illus span{position:absolute;font-size:64px;filter:drop-shadow(0 6px 10px rgba(30,64,175,.15))}
.welcome h1{font-size:34px;letter-spacing:-1px;text-align:center;margin:8px 0 4px}
.welcome .sub{text-align:center;color:var(--muted);margin:0 0 22px}
.feats{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;margin-bottom:26px}
.feat{text-align:center;font-size:12px;font-weight:600;color:var(--ink2)}
.feat .fi{width:52px;height:52px;border-radius:50%;display:grid;place-items:center;margin:0 auto 8px;color:#fff}
.free{text-align:center;font-size:12px;color:var(--muted);margin-top:12px}
.profile-top{display:flex;flex-direction:column;align-items:center;gap:8px;margin:6px 0 18px}

/* notifications */
.tabs{display:flex;gap:8px;margin-bottom:12px}
.tabs button{padding:7px 16px;border-radius:999px;border:1px solid var(--line);background:#fff;font-size:13px;font-weight:600;color:var(--muted)}
.tabs button.on{border-color:var(--blue);color:var(--blue);background:var(--blue-soft)}
.nitem{display:flex;gap:12px;padding:13px 0;border-bottom:1px solid var(--line);cursor:pointer}
.nitem:last-child{border-bottom:0}
.nitem .ni{width:42px;height:42px;border-radius:12px;display:grid;place-items:center;font-size:20px;flex:none}
.nitem b{font-size:14px;display:block}
.nitem .when{font-size:11px;color:var(--muted);white-space:nowrap}
.empty{text-align:center;color:var(--muted);padding:28px 10px;font-size:14px}

/* toasts + modal */
#toasts{position:fixed;top:calc(10px + env(safe-area-inset-top));left:12px;right:12px;z-index:200;display:flex;flex-direction:column;align-items:center;gap:8px;pointer-events:none}
.toast{background:#0f172a;color:#fff;padding:11px 15px;border-radius:12px;box-shadow:var(--shadow);max-width:420px;text-align:center;font-size:14px;border:1px solid #334155}
.modal-back{position:fixed;inset:0;background:rgba(2,6,23,.5);display:flex;align-items:flex-end;justify-content:center;z-index:150}
.modal{background:#fff;border-radius:22px 22px 0 0;padding:22px 18px calc(22px + env(safe-area-inset-bottom));width:100%;max-width:520px;max-height:92vh;overflow:auto}
.modal h2{margin:0 0 6px;font-size:20px}
.linkbox{background:#f8fafc;border:1px dashed #94a3b8;padding:11px;border-radius:12px;word-break:break-all;font-size:12px;margin-top:8px}

/* ================= voice room ================= */
.room{min-height:100vh;min-height:100dvh;background:radial-gradient(120% 60% at 50% 20%,#14233b 0%,#0a1322 60%);color:#fff;display:flex;flex-direction:column;max-width:520px;margin:auto}
.rhead{display:flex;align-items:center;gap:10px;padding:14px 14px 6px;padding-top:calc(14px + env(safe-area-inset-top))}
.rhead .back{width:38px;height:38px;border-radius:12px;display:grid;place-items:center;color:#fff}
.rhead .rt{flex:1;min-width:0}
.rhead .rt b{display:block;font-size:16px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.rhead .rt span{font-size:12px;color:#94a3b8;font-variant-numeric:tabular-nums}
.leavebtn{background:var(--red);color:#fff;font-weight:700;padding:8px 16px;border-radius:12px;font-size:14px}
.rstatus{margin:6px 14px 0;font-size:12px;color:#cbd5e1;background:rgba(255,255,255,.06);border-radius:10px;padding:8px 11px;text-align:center}
.stage{flex:1;padding:18px 14px 8px;display:flex;flex-direction:column;align-items:center}
.hostspot{display:flex;flex-direction:column;align-items:center;margin:8px 0 22px;position:relative}
.hostspot .waves{display:flex;align-items:center;gap:22px}
.wave{display:flex;align-items:center;gap:3px;opacity:.15;transition:opacity .15s}
.wave i{display:block;width:3px;border-radius:3px;background:#22c55e}
.wave i:nth-child(1){height:10px}.wave i:nth-child(2){height:22px}.wave i:nth-child(3){height:14px}
.speaking .wave{opacity:1}
.speaking .wave i{animation:eq .6s ease-in-out infinite alternate}
.speaking .wave i:nth-child(2){animation-delay:.2s}.speaking .wave i:nth-child(3){animation-delay:.4s}
@keyframes eq{from{transform:scaleY(.4)}to{transform:scaleY(1.1)}}
.pname{margin-top:8px;font-weight:700;font-size:14px;text-align:center;max-width:110px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.pname small{display:block;color:#93c5fd;font-weight:600;font-size:12px}
.pgrid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px 10px;width:100%}
.pcell{display:flex;flex-direction:column;align-items:center}
.ring{border-radius:50%;padding:3px;transition:box-shadow .15s}
.speaking .ring{box-shadow:0 0 0 3px #22c55e}
.av .mut{position:absolute;bottom:-2px;right:-2px;width:24px;height:24px;border-radius:50%;background:#ef4444;display:grid;place-items:center;border:2px solid #0a1322}
.av .hnd{position:absolute;top:-6px;right:-8px;font-size:20px}
.av .conn{position:absolute;inset:0;border-radius:50%;background:rgba(10,19,34,.55);display:grid;place-items:center;font-size:11px;font-weight:600}
.rcontrols{position:sticky;bottom:0;display:grid;grid-template-columns:repeat(4,1fr);padding:12px 8px calc(14px + env(safe-area-inset-bottom));background:linear-gradient(transparent,#0a1322 30%)}
.rc{display:flex;flex-direction:column;align-items:center;gap:6px;color:#cbd5e1;font-size:11px;font-weight:600}
.rc .cb{width:54px;height:54px;border-radius:50%;background:#1e293b;display:grid;place-items:center;color:#fff;position:relative}
.rc.on .cb{background:#334155}.rc.off .cb{background:var(--red)}.rc.raised .cb{background:#d97706}
.rc .badge-n{position:absolute;top:-3px;right:-3px;background:var(--red);color:#fff;font-size:11px;min-width:19px;height:19px;border-radius:10px;display:grid;place-items:center;padding:0 4px;border:2px solid #0a1322}

/* bottom sheets inside room (white, like mockup screens 8 & 9) */
.sheet-back{position:fixed;inset:0;background:rgba(2,6,23,.45);z-index:60;display:flex;align-items:flex-end;justify-content:center}
.sheet{background:#fff;color:var(--ink);width:100%;max-width:520px;height:82vh;height:82dvh;border-radius:22px 22px 0 0;display:flex;flex-direction:column}
.sheet-h{display:flex;align-items:center;padding:14px 14px 10px;border-bottom:1px solid var(--line)}
.sheet-h b{flex:1;text-align:center;font-size:16px}
.sheet-b{flex:1;overflow-y:auto;padding:10px 16px}
.plabel{font-size:13px;font-weight:700;color:var(--ink2);margin:10px 0 4px}
.prow{display:flex;align-items:center;gap:12px;padding:9px 0}
.prow .grow b{display:block;font-size:14px}.prow .grow span{font-size:12px;color:var(--muted)}
.prow .mic-on{color:var(--blue)}.prow .mic-off{color:var(--red)}
.msg{display:flex;gap:9px;margin:10px 0;align-items:flex-start}
.msg .bub{background:#f1f5f9;border-radius:4px 14px 14px 14px;padding:8px 11px;max-width:78%;font-size:14px;word-wrap:break-word}
.msg .who{font-size:12px;font-weight:700;margin-bottom:2px}.msg .who span{font-weight:500;color:var(--muted);margin-left:6px}
.msg.mine{justify-content:flex-end}
.msg.mine .bub{background:var(--blue);color:#fff;border-radius:14px 4px 14px 14px}
.msg.mine .who span{color:#c7d7fe}
.sys{text-align:center;font-size:12px;color:var(--muted);margin:8px 0}
.chatin{display:flex;gap:8px;padding:10px 12px calc(10px + env(safe-area-inset-bottom));border-top:1px solid var(--line)}
.chatin input{flex:1;min-width:0;border:1px solid var(--line);border-radius:12px;padding:11px 13px;font-size:16px;outline:none}
.chatin button{width:46px;border-radius:12px;background:var(--blue);color:#fff;display:grid;place-items:center}

@media (min-width:521px){.nav-inner{border-left:1px solid var(--line);border-right:1px solid var(--line)}}

.netinfo{margin:6px auto 0;font-size:11px;font-weight:600;padding:3px 10px;border-radius:999px;color:#cbd5e1;text-align:center}
.netinfo:empty{display:none}
.netinfo.good{background:rgba(34,197,94,.15);color:#86efac}.netinfo.ok{background:rgba(234,179,8,.15);color:#fde68a}.netinfo.bad{background:rgba(239,68,68,.18);color:#fca5a5}