:root{
  --bg:#f5f6fb; --ink:#1f2238; --muted:#6b7088;
  --primary:#5b4bdb; --primary-d:#4636c4;
  --accent:#ff6b6b; --card:#ffffff; --line:#e6e7f0;
  --good:#2bb673; --hard:#f0a92b; --again:#e8503a; --easy:#3a8de8;
  --shadow:0 6px 24px rgba(31,34,56,.08);
}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Arial,sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.5}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}

.nav{display:flex;align-items:center;justify-content:space-between;
  padding:14px 24px;background:var(--card);border-bottom:1px solid var(--line)}
.brand{font-weight:800;font-size:1.15rem;color:var(--ink)}
.nav nav{display:flex;align-items:center;gap:18px}
.nav .who{color:var(--muted);font-size:.92rem}
.nav .ghost{color:var(--muted)}

.container{max-width:880px;margin:0 auto;padding:32px 24px}

h1{font-size:2rem;margin:0 0 6px}
.muted{color:var(--muted)}
.center{text-align:center}
.error{background:#fdecec;color:#b3261e;padding:10px 14px;border-radius:10px}
.ok{background:#e7f7ee;color:#1c7a4b;padding:10px 14px;border-radius:10px;font-weight:600}
code{background:#eef0f7;padding:2px 6px;border-radius:6px;font-size:.92em}
textarea{width:100%;padding:11px 12px;margin-top:6px;border:1px solid var(--line);
  border-radius:10px;font-size:1rem;font-family:inherit;background:#fff;resize:vertical}
textarea:focus{outline:2px solid var(--primary);border-color:var(--primary)}

/* hero */
.hero{text-align:center;padding:28px 0 8px}
.hero h1{font-size:2.6rem}
.lead{font-size:1.15rem;color:var(--muted);max-width:620px;margin:10px auto 22px}
.cta{display:flex;gap:12px;justify-content:center;flex-wrap:wrap;margin:18px 0}

/* buttons */
.btn{display:inline-block;padding:11px 20px;border-radius:12px;border:1px solid var(--line);
  background:var(--card);color:var(--ink);font-weight:600;cursor:pointer;font-size:1rem}
.btn:hover{text-decoration:none;border-color:#c9cbe0}
.btn.primary{background:var(--primary);border-color:var(--primary);color:#fff}
.btn.primary:hover{background:var(--primary-d)}
.btn.ghost{background:transparent;color:var(--muted)}
.btn.wide{width:100%}
.big-btn{font-size:1.15rem;padding:14px 28px}

/* cards grid */
.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;margin-top:28px}
.grid-2{display:grid;grid-template-columns:repeat(2,1fr);gap:18px;margin-top:24px}
.card{background:var(--card);border:1px solid var(--line);border-radius:16px;
  padding:22px;box-shadow:var(--shadow)}
.card .ico{font-size:2rem;margin-bottom:8px}
.card h3{margin:6px 0}

/* forms */
.form-card{background:var(--card);border:1px solid var(--line);border-radius:16px;
  padding:26px;max-width:420px;margin:18px auto;box-shadow:var(--shadow)}
.form-card.center{text-align:center}
label{display:block;margin:12px 0;font-weight:600}
input,select{width:100%;padding:11px 12px;margin-top:6px;border:1px solid var(--line);
  border-radius:10px;font-size:1rem;background:#fff;font-weight:400}
input:focus,select:focus{outline:2px solid var(--primary);border-color:var(--primary)}
.mt{margin-top:12px}

/* dashboard */
.dash-head{margin-bottom:18px}
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:14px}
.stat{background:var(--card);border:1px solid var(--line);border-radius:14px;
  padding:18px;text-align:center;box-shadow:var(--shadow)}
.stat .num{font-size:2rem;font-weight:800}
.stat .lbl{color:var(--muted);font-size:.85rem}
.stat.accent{background:var(--primary);border-color:var(--primary)}
.stat.accent .num,.stat.accent .lbl{color:#fff}
.goal{margin:24px 0}
.goal-row{display:flex;justify-content:space-between;color:var(--muted);margin-bottom:6px}
.bar{height:12px;background:#e9eaf4;border-radius:8px;overflow:hidden}
.bar-fill{height:100%;background:var(--good);border-radius:8px;transition:width .3s}
.done{font-size:1.1rem}

/* study flashcard */
.flash{background:var(--card);border:1px solid var(--line);border-radius:20px;
  box-shadow:var(--shadow);padding:54px 24px;margin:22px auto;max-width:560px;text-align:center}
.flash-front{font-size:2.4rem;font-weight:700}
.flash-back{font-size:1.6rem;color:var(--primary);margin-top:18px;
  border-top:1px solid var(--line);padding-top:18px}
.rate{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;max-width:560px;margin:16px auto}
.rate .btn{color:#fff;border:none}
.rate-1{background:var(--again)} .rate-2{background:var(--hard)}
.rate-3{background:var(--good)} .rate-4{background:var(--easy)}

/* table */
.tbl{width:100%;border-collapse:collapse;background:var(--card);border-radius:14px;
  overflow:hidden;box-shadow:var(--shadow);margin-top:14px}
.tbl th,.tbl td{padding:12px 14px;text-align:left;border-bottom:1px solid var(--line)}
.tbl th{background:#f0f1f9;font-size:.85rem;text-transform:uppercase;color:var(--muted)}

@media(max-width:680px){
  .grid-3,.grid-2,.stats{grid-template-columns:1fr 1fr}
  .rate{grid-template-columns:1fr 1fr}
}