/* ============ Design System (dùng chung mọi trang) ============ */
* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --bg: #f4f6fb;
  --card: #ffffff;
  --primary: #4f6ef7;
  --primary-dark: #3a55d9;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #e5e7eb;
  --todo: #f59e0b;
  --doing: #3b82f6;
  --done: #10b981;
  --danger: #ef4444;
  --shadow: 0 10px 30px rgba(31, 41, 55, .08);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
}

a { color: inherit; text-decoration: none; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  font-size: 14px; font-weight: 600; font-family: inherit;
  padding: 11px 20px; border-radius: 10px; border: none; cursor: pointer;
  transition: background .15s, transform .05s, box-shadow .15s;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-ghost { background: transparent; color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--bg); }
.btn-block { width: 100%; }
.btn-lg { padding: 14px 28px; font-size: 15px; }

/* ---------- Inputs ---------- */
.field { margin-bottom: 16px; }
.field label { display: block; font-size: 13px; font-weight: 600; margin-bottom: 6px; color: var(--text); }
input, select, textarea {
  width: 100%; font-size: 14px; font-family: inherit;
  padding: 11px 13px; border-radius: 10px;
  border: 1px solid var(--border); outline: none; background: #fff;
  transition: border-color .15s, box-shadow .15s;
}
input:focus, select:focus, textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79, 110, 247, .15);
}

/* ---------- Brand / logo ---------- */
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; }
.brand .logo {
  width: 34px; height: 34px; border-radius: 9px;
  background: var(--primary); color: #fff;
  display: grid; place-items: center; font-weight: 800; font-size: 16px;
}

/* ---------- Helpers ---------- */
.muted { color: var(--muted); }
.center { text-align: center; }
.hidden { display: none !important; }
.alert {
  font-size: 13px; padding: 10px 14px; border-radius: 8px; margin-bottom: 16px;
}
.alert-error { background: #fee2e2; color: #b91c1c; }
.alert-ok { background: #dcfce7; color: #15803d; }