*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --primary: #4F46E5; --primary-h: #4338CA;
  --know: #059669;    --know-h: #047857;
  --fuzzy: #D97706;   --fuzzy-h: #B45309;
  --forget: #DC2626;  --forget-h: #B91C1C;
  --bg: #F3F4F6;      --card: #FFFFFF;
  --text: #111827;    --text2: #6B7280;
  --border: #E5E7EB;  --radius: 12px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.6;
  max-width: 480px; margin: 0 auto; min-height: 100vh; padding-bottom: 40px;
}

/* ── Top bar ── */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 16px; background: var(--card); border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
}
.topbar h1 { font-size: 1.1rem; font-weight: 600; }
.topbar button { background: none; border: none; font-size: 0.9rem; color: var(--text2); cursor: pointer; }

/* ── Pages ── */
.page { padding: 16px; }
.page.hidden { display: none; }

/* ── Login ── */
.login-box { max-width: 360px; margin: 60px auto 0; text-align: center; }
.login-box h1 { font-size: 1.6rem; margin-bottom: 4px; }
.login-box .sub { color: var(--text2); font-size: 0.9rem; margin-bottom: 24px; }
.login-box input {
  display: block; width: 100%; padding: 12px 16px; margin-bottom: 12px;
  border: 1px solid var(--border); border-radius: var(--radius); font-size: 1rem;
  outline: none; transition: border-color 0.15s;
}
.login-box input:focus { border-color: var(--primary); }
.login-btns { display: flex; gap: 10px; }
.login-btns button { flex: 1; }
.login-error { color: var(--forget); font-size: 0.85rem; margin-top: 8px; min-height: 20px; }

/* ── Buttons ── */
.btn {
  display: inline-block; padding: 10px 20px; border: none; border-radius: var(--radius);
  font-size: 0.95rem; font-weight: 500; cursor: pointer; text-align: center;
  transition: background 0.15s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-h); }
.btn-know { background: var(--know); color: #fff; }
.btn-know:hover { background: var(--know-h); }
.btn-fuzzy { background: var(--fuzzy); color: #fff; }
.btn-fuzzy:hover { background: var(--fuzzy-h); }
.btn-forget { background: var(--forget); color: #fff; }
.btn-forget:hover { background: var(--forget-h); }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }

/* ── Home: due card ── */
.due-card {
  background: var(--primary); color: #fff; border-radius: var(--radius);
  padding: 20px; text-align: center; cursor: pointer; margin-bottom: 20px;
}
.due-num { font-size: 2.4rem; font-weight: 700; }
.due-label { font-size: 0.9rem; opacity: 0.85; margin-top: 2px; }

/* ── Section headers ── */
.sec-title {
  font-size: 1rem; font-weight: 600; margin-bottom: 10px;
  display: flex; align-items: center; gap: 6px;
}

/* ── Task list ── */
.task-item {
  display: flex; align-items: center; gap: 10px; padding: 10px 12px;
  background: var(--card); border-radius: 8px; margin-bottom: 6px;
  font-size: 0.92rem;
}
.task-item.done .task-content { text-decoration: line-through; color: var(--text2); }
.task-item input[type=checkbox] { width: 18px; height: 18px; accent-color: var(--primary); cursor: pointer; }
.task-content { flex: 1; }
.task-dd { font-size: 0.8rem; white-space: nowrap; }
.dd-ok { color: var(--know); } .dd-warn { color: var(--fuzzy); } .dd-over { color: var(--forget); }
.task-del { background: none; border: none; color: var(--text2); font-size: 1.2rem; cursor: pointer; padding: 0 4px; }
.task-empty { color: var(--text2); font-size: 0.9rem; text-align: center; padding: 16px; }

/* ── Add-task row ── */
.add-row { display: flex; gap: 8px; margin-top: 10px; }
.add-row input[type=text] { flex: 1; padding: 10px 12px; border: 1px solid var(--border); border-radius: var(--radius); font-size: 0.9rem; outline: none; }
.add-row input[type=text]:focus { border-color: var(--primary); }
.add-row input[type=date] { padding: 10px; border: 1px solid var(--border); border-radius: var(--radius); font-size: 0.85rem; outline: none; }
.add-row button { white-space: nowrap; }

/* ── Groups ── */
.group-item {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 16px; background: var(--card); border-radius: var(--radius);
  margin-bottom: 8px; cursor: pointer;
}
.group-info { flex: 1; }
.group-name { font-weight: 500; }
.group-count { font-size: 0.82rem; color: var(--text2); }
.group-del { background: none; border: none; color: var(--forget); font-size: 0.85rem; cursor: pointer; }
.add-group-row { display: flex; gap: 8px; margin-top: 16px; }
.add-group-row input { flex: 1; padding: 10px 12px; border: 1px solid var(--border); border-radius: var(--radius); font-size: 0.9rem; outline: none; }
.add-group-row input:focus { border-color: var(--primary); }

/* ── Cards ── */
.card-item {
  padding: 14px 16px; background: var(--card); border-radius: var(--radius);
  margin-bottom: 8px; position: relative;
}
.card-item-front { font-weight: 600; margin-bottom: 2px; }
.card-item-back { color: var(--text2); font-size: 0.9rem; margin-bottom: 4px; }
.card-item-meta { font-size: 0.78rem; color: var(--text2); }
.card-due { color: var(--forget); font-weight: 500; }
.card-next { color: var(--know); }
.card-del { position: absolute; right: 12px; top: 14px; background: none; border: none; color: var(--text2); font-size: 0.85rem; cursor: pointer; }

/* ── New card ── */
.new-card-form { display: flex; flex-direction: column; gap: 12px; margin-top: 12px; }
.new-card-form textarea {
  width: 100%; padding: 12px; border: 1px solid var(--border); border-radius: var(--radius);
  font-size: 0.95rem; font-family: inherit; outline: none; resize: vertical; min-height: 80px;
}
.new-card-form textarea:focus { border-color: var(--primary); }

/* ── Review ── */
.review-select h2 { font-size: 1rem; margin-bottom: 12px; }
.group-checks { margin-bottom: 16px; }
.group-check {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 14px; background: var(--card); border-radius: 8px;
  margin-bottom: 6px; cursor: pointer; font-size: 0.9rem;
}
.group-check input { width: 17px; height: 17px; accent-color: var(--primary); }

.review-progress { text-align: center; font-size: 0.85rem; color: var(--text2); margin-bottom: 12px; }

.card-face {
  background: var(--card); border-radius: var(--radius); padding: 32px 20px;
  text-align: center; min-height: 160px; display: flex; flex-direction: column;
  align-items: center; justify-content: center; cursor: pointer;
  border: 2px solid var(--border); margin-bottom: 16px;
}
.card-face.flipped { cursor: default; text-align: left; align-items: flex-start; }
.card-front-content { font-size: 1.2rem; font-weight: 600; }
.card-hint { font-size: 0.82rem; color: var(--text2); margin-top: 12px; }
.card-front-label { font-size: 0.82rem; color: var(--text2); margin-bottom: 10px; }
.card-back-content { font-size: 1.05rem; }

.review-buttons { display: flex; gap: 8px; }
.review-buttons .btn { flex: 1; padding: 14px 8px; font-size: 0.9rem; }

.review-done { text-align: center; padding: 40px 20px; }
.review-done p { font-size: 1.1rem; margin-bottom: 16px; }

.review-empty { text-align: center; padding: 60px 20px; color: var(--text2); }
.review-empty button { margin-top: 12px; }

/* ── Bottom nav ── */
.bottom-nav {
  display: flex; justify-content: space-around;
  background: var(--card); border-top: 1px solid var(--border);
  padding: 8px 0 calc(8px + env(safe-area-inset-bottom));
  position: fixed; bottom: 0; left: 0; right: 0; max-width: 480px; margin: 0 auto; z-index: 10;
}
.bottom-nav a {
  text-decoration: none; color: var(--text2); font-size: 0.75rem;
  display: flex; flex-direction: column; align-items: center; gap: 2px;
}
.bottom-nav a .nav-icon { font-size: 1.3rem; }
.bottom-nav a.active { color: var(--primary); }

.page { padding-bottom: 80px; }
#page-login, #page-new { padding-bottom: 80px; }

/* ── Watermark ── */
.watermark {
  position: fixed; bottom: 70px; right: 20px;
  font-size: 0.75rem; color: #9CA3AF; pointer-events: none;
  z-index: 1; user-select: none;
}

/* ── Misc ── */
button { font-family: inherit; }