:root{
  --bg:#f1f5f9; --card:#ffffff; --ink:#0f172a; --muted:#64748b;
  --primary:#4f46e5; --primary-d:#4338ca;
  --known:#16a34a; --known-d:#15803d; --unknown:#ef4444; --unknown-d:#dc2626;
  --line:#e2e8f0; --shadow:0 10px 30px rgba(2,6,23,.08);
  --radius:18px;
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;height:100%}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Hiragino Sans GB","Microsoft YaHei",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg); color:var(--ink);
  -webkit-font-smoothing:antialiased; line-height:1.5;
}
#app{
  min-height:100dvh; max-width:520px; margin:0 auto;
  padding:env(safe-area-inset-top) 16px calc(env(safe-area-inset-bottom) + 16px);
  display:flex; flex-direction:column;
}
.view{flex:1; display:flex; flex-direction:column}
.hidden{display:none !important}

/* loading */
#view-loading{align-items:center;justify-content:center}
.spinner{width:38px;height:38px;border:4px solid var(--line);border-top-color:var(--primary);border-radius:50%;animation:spin .8s linear infinite}
@keyframes spin{to{transform:rotate(360deg)}}

/* ---------- auth ---------- */
#view-auth{justify-content:center;gap:22px}
.auth-box{background:var(--card);border-radius:24px;box-shadow:var(--shadow);padding:28px 22px}
.brand{text-align:center;margin-bottom:18px}
.brand-logo{
  display:inline-flex;align-items:center;justify-content:center;
  width:60px;height:60px;border-radius:16px;margin-bottom:10px;
  background:linear-gradient(135deg,var(--primary),#7c73f0);
  color:#fff;font-weight:800;letter-spacing:.5px;font-size:18px;
  box-shadow:0 8px 18px rgba(79,70,229,.35)
}
.brand h1{font-size:22px;margin:6px 0 4px}
.brand-sub{color:var(--muted);font-size:13px;margin:0}
.tabs{display:flex;background:#eef0f5;border-radius:12px;padding:4px;margin-bottom:16px}
.tab{flex:1;border:0;background:transparent;padding:10px;border-radius:9px;font-size:15px;font-weight:600;color:var(--muted);cursor:pointer}
.tab.active{background:#fff;color:var(--primary);box-shadow:0 2px 6px rgba(2,6,23,.08)}
#auth-form{display:flex;flex-direction:column;gap:12px}
input{
  width:100%;padding:14px 14px;border:1.5px solid var(--line);border-radius:12px;
  font-size:16px;background:#fff;color:var(--ink);outline:none;transition:border-color .15s
}
input:focus{border-color:var(--primary)}
.err{color:var(--unknown-d);font-size:13px;min-height:18px;text-align:center}
.footer-note{text-align:center;color:var(--muted);font-size:12px}

/* ---------- buttons ---------- */
.btn{
  width:100%;border:0;border-radius:14px;padding:15px;font-size:17px;font-weight:700;
  cursor:pointer;transition:transform .06s ease, filter .15s, background .15s;color:#fff
}
.btn:active{transform:scale(.97)}
.btn:disabled{opacity:.6}
.btn-primary{background:var(--primary)}
.btn-primary:active{background:var(--primary-d)}
.btn-known{background:var(--known)}
.btn-known:active{background:var(--known-d)}
.btn-unknown{background:var(--unknown)}
.btn-unknown:active{background:var(--unknown-d)}
.btn-ghost{background:#fff;color:var(--primary);border:1.5px solid var(--primary)}
.btn-revise{background:#fff;color:var(--unknown-d);border:1.5px solid #f3c4c4;font-size:15px;font-weight:600;padding:12px;margin-bottom:10px}
.btn-revise:active{background:#fdecec}
.link{background:none;border:0;color:var(--muted);font-size:14px;cursor:pointer;padding:6px}

/* ---------- study ---------- */
.topbar{display:flex;align-items:center;justify-content:space-between;padding:8px 2px 4px}
.hello{font-size:15px;color:var(--muted)}
.hello b{color:var(--ink)}
.stats{display:flex;gap:10px;margin:10px 0}
.stat{flex:1;background:var(--card);border-radius:14px;padding:12px 6px;text-align:center;box-shadow:var(--shadow)}
.stat-num{font-size:24px;font-weight:800;color:var(--primary)}
.stat-label{font-size:12px;color:var(--muted);margin-top:2px}
.round-bar{margin:6px 2px 14px}
.round-bar-label{font-size:12px;color:var(--muted);margin-bottom:6px}
.progress{height:8px;background:#e6e8ef;border-radius:99px;overflow:hidden}
.progress-fill{height:100%;width:0;background:linear-gradient(90deg,var(--primary),#7c73f0);border-radius:99px;transition:width .3s}

.card{
  flex:1;background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);
  padding:26px 20px;display:flex;flex-direction:column;align-items:center;
  justify-content:center;text-align:center;min-height:340px
}
.word{font-size:clamp(34px,9vw,46px);font-weight:800;letter-spacing:.5px;word-break:break-word}
.streak{display:flex;gap:8px;margin:16px 0 6px;height:14px}
.dot{width:13px;height:13px;border-radius:50%;background:#dfe3ee;border:1.5px solid #cdd3e3}
.dot.on{background:var(--known);border-color:var(--known)}

.phase{width:100%;margin-top:26px}
.hint{color:var(--muted);font-size:14px;margin:10px 0 14px}
.btn-row{display:flex;gap:12px}
.btn-row .btn{flex:1}

.reveal{margin:6px 0 4px;font-size:19px;line-height:1.7}
.pos{display:inline-block;background:#eef0fb;color:var(--primary-d);font-size:14px;font-weight:700;
  padding:2px 9px;border-radius:8px;margin-right:8px;vertical-align:middle}
.def{color:var(--ink)}
.note{font-size:13px;min-height:20px;margin:10px 0 16px}
.note.known{color:var(--known-d)}
.note.unknown{color:var(--unknown-d)}
.note.grad{color:var(--primary-d);font-weight:700}

/* ---------- done ---------- */
#view-done{align-items:center;justify-content:center}
.done-box{background:var(--card);border-radius:24px;box-shadow:var(--shadow);padding:34px 24px;text-align:center;width:100%}
.done-emoji{font-size:54px}
.done-box h2{margin:8px 0}
.done-box p{color:var(--muted);margin:6px 0 12px}
.done-stats{margin:8px 0 20px;font-size:15px}
.done-box .btn{margin-bottom:12px}