:root{
  --bg:#f6f7fb; --card:#ffffff; --ink:#111827; --muted:#6b7280; --line:#e5e7eb;
  --brand:#4f46e5; --brand-soft:#eef2ff; --ok:#16a34a; --ok-soft:#dcfce7;
  --bad:#dc2626; --bad-soft:#fee2e2; --warn:#f59e0b;
  --shadow:0 1px 2px rgba(16,24,40,.06),0 8px 24px -12px rgba(16,24,40,.18);
  --r:16px; --tab-h:64px;
  --safe-b:env(safe-area-inset-bottom,0px);
  color-scheme:light dark;
}
@media (prefers-color-scheme:dark){
  :root{
    --bg:#0b1020; --card:#151b2e; --ink:#e8eaf2; --muted:#9aa3b8; --line:#25304a;
    --brand:#818cf8; --brand-soft:#1e2440; --ok:#4ade80; --ok-soft:#123322;
    --bad:#f87171; --bad-soft:#3a1717;
    --shadow:0 1px 2px rgba(0,0,0,.4),0 8px 24px -12px rgba(0,0,0,.6);
  }
}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
html,body{margin:0;padding:0}
body{
  background:var(--bg);color:var(--ink);
  font:16px/1.55 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  overscroll-behavior-y:none;
}
button,input,select{font:inherit;color:inherit}
button{cursor:pointer;border:0;background:none}
h1,h2,h3,h4{margin:0;line-height:1.25;letter-spacing:-.01em}
p{margin:0 0 .75em}
a{color:var(--brand)}

/* ---------- LAYOUT ---------- */
#app{max-width:900px;margin:0 auto;padding:0 16px calc(var(--tab-h) + var(--safe-b) + 24px)}
header.top{
  position:sticky;top:0;z-index:40;background:var(--bg);
  padding:14px 0 10px;display:flex;align-items:center;gap:12px;
}
header.top .t{flex:1;min-width:0}
header.top h1{font-size:22px;font-weight:800}
header.top .sub{font-size:13px;color:var(--muted)}
.streak{
  background:var(--card);border:1px solid var(--line);border-radius:999px;
  padding:6px 12px;font-size:13px;font-weight:700;white-space:nowrap;box-shadow:var(--shadow)
}
.view{display:none;animation:in .18s ease}
.view.on{display:block}
@keyframes in{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}

/* ---------- TABS ---------- */
nav.tabs{
  position:fixed;left:0;right:0;bottom:0;z-index:50;
  background:color-mix(in srgb,var(--card) 92%,transparent);
  backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);
  border-top:1px solid var(--line);
  padding-bottom:var(--safe-b);
  display:grid;grid-template-columns:repeat(5,1fr)
}
nav.tabs button{
  height:var(--tab-h);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:3px;
  font-size:11px;font-weight:600;color:var(--muted);transition:color .15s
}
nav.tabs button .ic{font-size:21px;line-height:1}
nav.tabs button.on{color:var(--brand)}
nav.tabs button.on .ic{transform:translateY(-1px)}
@media(min-width:860px){
  :root{--tab-h:58px}
  nav.tabs{
    top:0;bottom:auto;border-top:0;border-bottom:1px solid var(--line);padding-bottom:0;
    position:fixed;justify-content:center
  }
  nav.tabs button{height:var(--tab-h);flex-direction:row;gap:8px;font-size:14.5px}
  nav.tabs{grid-template-columns:repeat(5,minmax(0,168px))}
  #app{padding-bottom:48px;padding-top:calc(var(--tab-h) + 4px)}
  header.top{top:var(--tab-h)}
}

/* ---------- CARDS ---------- */
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--r);
  padding:16px;margin:0 0 12px;box-shadow:var(--shadow)
}
.card.tight{padding:12px 14px}
.grid{display:grid;gap:12px}
.grid.two{grid-template-columns:1fr 1fr}
@media(min-width:640px){.grid.auto{grid-template-columns:1fr 1fr}}
.tile{
  display:flex;align-items:center;gap:12px;width:100%;text-align:left;
  background:var(--card);border:1px solid var(--line);border-radius:var(--r);
  padding:14px;box-shadow:var(--shadow);transition:transform .12s
}
.tile:active{transform:scale(.98)}
.tile .em{font-size:28px;width:44px;height:44px;display:grid;place-items:center;border-radius:12px;flex:none}
.tile .tx{flex:1;min-width:0}
.tile .tx b{display:block;font-size:15px}
.tile .tx span{font-size:13px;color:var(--muted)}
.tile .go{color:var(--muted);font-size:18px}
.bar{height:6px;background:var(--line);border-radius:99px;overflow:hidden;margin-top:8px}
.bar i{display:block;height:100%;background:var(--brand);border-radius:99px;transition:width .4s}
.pill{
  display:inline-block;padding:3px 9px;border-radius:999px;font-size:12px;font-weight:700;
  background:var(--brand-soft);color:var(--brand)
}
.muted{color:var(--muted)}
.small{font-size:13px}
.center{text-align:center}
.row{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.spread{display:flex;justify-content:space-between;align-items:center;gap:10px}

/* ---------- BUTTONS ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  background:var(--brand);color:#fff;border-radius:12px;padding:12px 18px;
  font-weight:700;font-size:15px;transition:transform .12s,opacity .15s
}
.btn:active{transform:scale(.97)}
.btn.ghost{background:var(--card);color:var(--ink);border:1px solid var(--line)}
.btn.sm{padding:8px 13px;font-size:14px;border-radius:10px}
.btn.wide{width:100%}
.btn[disabled]{opacity:.45;pointer-events:none}
.back{font-size:14px;font-weight:700;color:var(--brand);padding:8px 0;display:inline-block}

/* ---------- FLASHCARDS ---------- */
.deck{perspective:1200px;margin:8px 0 14px}
.fc{
  position:relative;width:100%;min-height:230px;transform-style:preserve-3d;
  transition:transform .5s cubic-bezier(.4,.2,.2,1);cursor:pointer
}
.fc.flip{transform:rotateY(180deg)}
.fc .face{
  position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;
  background:var(--card);border:1px solid var(--line);border-radius:20px;box-shadow:var(--shadow);
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:10px;padding:24px;text-align:center
}
.fc .face.b{transform:rotateY(180deg)}
.fc .pic{font-size:48px;line-height:1}
.fc .word{font-size:24px;font-weight:800}
.fc .hintline{font-size:12px;color:var(--muted)}
.speak{
  width:44px;height:44px;border-radius:50%;background:var(--brand-soft);color:var(--brand);
  display:grid;place-items:center;font-size:19px;flex:none
}

/* ---------- QUIZ ---------- */
.opt{
  display:block;width:100%;text-align:left;background:var(--card);border:2px solid var(--line);
  border-radius:14px;padding:14px 16px;margin-bottom:10px;font-weight:600;transition:.15s
}
.opt:active{transform:scale(.985)}
.opt.ok{border-color:var(--ok);background:var(--ok-soft)}
.opt.bad{border-color:var(--bad);background:var(--bad-soft)}
.opt.dim{opacity:.45}
.qtext{font-size:20px;font-weight:800;margin:6px 0 16px;line-height:1.35}
.qmeta{font-size:13px;color:var(--muted);margin-bottom:2px}
input[type=text]{
  width:100%;background:var(--card);border:2px solid var(--line);border-radius:12px;
  padding:13px 14px;outline:none
}
input[type=text]:focus{border-color:var(--brand)}
input[type=text].ok{border-color:var(--ok);background:var(--ok-soft)}
input[type=text].bad{border-color:var(--bad);background:var(--bad-soft)}
.fb{border-radius:12px;padding:12px 14px;margin-top:10px;font-size:14px;font-weight:600}
.fb.ok{background:var(--ok-soft);color:var(--ok)}
.fb.bad{background:var(--bad-soft);color:var(--bad)}

/* ---------- GRAMMAR ---------- */
.gtable{width:100%;border-collapse:collapse;font-size:14px;margin:10px 0 4px;display:block;overflow-x:auto}
.gtable th,.gtable td{border:1px solid var(--line);padding:8px 10px;text-align:left;white-space:nowrap}
.gtable th{background:var(--brand-soft);font-weight:700;font-size:13px}
.tblwrap{position:relative;overflow-x:auto;-webkit-overflow-scrolling:touch;margin:10px 0 4px}
.tblwrap .gtable{display:table;margin:0;min-width:100%}
.scrollhint{font-size:12px;color:var(--muted);margin:0 0 6px}
@media(min-width:700px){.scrollhint{display:none}}
.tip{background:var(--brand-soft);border-radius:12px;padding:12px 14px;font-size:14px;margin:12px 0 0}
.formula{font-weight:800;font-size:15px;text-align:center;line-height:2.2}
.formula span{padding:5px 9px;border-radius:8px;margin:0 2px;white-space:nowrap;display:inline-block}
.b1{background:#fee2e2;color:#991b1b}.b2{background:#dbeafe;color:#1e40af}
.b3{background:#dcfce7;color:#166534}.b4{background:#fef3c7;color:#92400e}

/* ---------- BUILDER ---------- */
.slot{margin-bottom:14px}
.slot h4{font-size:13px;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);margin-bottom:8px}
.chips{display:flex;gap:7px;flex-wrap:wrap}
.chip{
  border:1.5px solid var(--line);background:var(--card);border-radius:999px;
  padding:7px 13px;font-size:14px;font-weight:600;transition:.12s
}
.chip.on{background:var(--brand);border-color:var(--brand);color:#fff}
.output{
  background:var(--brand-soft);border-radius:14px;padding:16px;margin-top:4px;
  font-size:19px;font-weight:700;line-height:1.5;min-height:60px
}
.output .en{display:block;font-size:14px;font-weight:500;color:var(--muted);margin-top:6px}

/* ---------- READING ---------- */
.bubble{
  background:var(--card);border:1px solid var(--line);border-radius:16px;padding:14px;
  margin-bottom:10px;box-shadow:var(--shadow)
}
.bubble .who{font-weight:800;font-size:14px;margin-bottom:5px;color:var(--brand)}
details.acc{border:1px solid var(--line);border-radius:12px;padding:0;margin-bottom:8px;background:var(--card);overflow:hidden}
details.acc>summary{padding:13px 14px;font-weight:700;font-size:15px;cursor:pointer;list-style:none;display:flex;justify-content:space-between;gap:10px}
details.acc>summary::-webkit-details-marker{display:none}
details.acc>summary::after{content:'▾';color:var(--muted);transition:.2s}
details.acc[open]>summary::after{transform:rotate(180deg)}
details.acc .body{padding:0 14px 14px;font-size:14.5px}
.tf{display:flex;gap:8px;margin-left:auto}
.tfbtn{border:2px solid var(--line);border-radius:9px;padding:5px 13px;font-weight:800;font-size:13px}
.tfbtn.ok{border-color:var(--ok);background:var(--ok-soft);color:var(--ok)}
.tfbtn.bad{border-color:var(--bad);background:var(--bad-soft);color:var(--bad)}

/* ---------- MISC ---------- */
.check{display:flex;gap:10px;align-items:flex-start;padding:11px 0;border-bottom:1px solid var(--line);font-size:14.5px}
.check:last-child{border-bottom:0}
.box{
  width:22px;height:22px;border-radius:6px;border:2px solid var(--line);flex:none;margin-top:1px;
  display:grid;place-items:center;font-size:14px;color:#fff
}
.box.on{background:var(--ok);border-color:var(--ok)}
.confetti{position:fixed;inset:0;pointer-events:none;z-index:99}
.toast{
  position:fixed;left:50%;transform:translateX(-50%);bottom:calc(var(--tab-h) + var(--safe-b) + 16px);
  background:var(--ink);color:var(--bg);padding:11px 18px;border-radius:999px;font-size:14px;font-weight:700;
  z-index:80;opacity:0;transition:opacity .2s
}
.toast.on{opacity:1}
.instbar{
  background:var(--brand);color:#fff;border-radius:14px;padding:13px 15px;margin-bottom:12px;
  display:flex;gap:12px;align-items:center;font-size:14px
}
.instbar button{background:#fff;color:var(--brand);border-radius:9px;padding:7px 13px;font-weight:800;font-size:13px;flex:none}