/* base.css - Bien mau dung chung + reset nhe. Thiet ke mobile-first.
   Cac bien o :root giup doi mau toan he thong o 1 cho. */
:root {
  --bg: #f0f2f5;
  --surface: #ffffff;
  --surface-2: #f7f9fc;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --text: #1f2937;
  --text-muted: #6b7280;
  --border: #e5e7eb;
  --danger: #dc2626;
  --success: #16a34a;
  --warning: #d97706;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,.08), 0 4px 16px rgba(0,0,0,.04);
  --header-h: 56px;
  /* Chieu cao thuc cua viewport tren mobile (set bang JS de tranh loi thanh dia chi). */
  --vh: 1vh;
}

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

html, body {
  height: 100%;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  -webkit-text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
}

button { font-family: inherit; cursor: pointer; border: none; }
input, textarea, select { font-family: inherit; font-size: 16px; } /* 16px tranh iOS tu zoom */

.btn-primary {
  background: var(--primary); color: #fff; padding: 12px 16px;
  border-radius: var(--radius); font-size: 15px; font-weight: 600;
  transition: background .15s ease;
}
.btn-primary:hover { background: var(--primary-dark); }
.btn-primary:disabled { opacity: .6; cursor: not-allowed; }

.btn-secondary {
  background: var(--surface-2); color: var(--text); padding: 10px 14px;
  border: 1px solid var(--border); border-radius: var(--radius); font-weight: 500;
}

.muted { color: var(--text-muted); }
.error { color: var(--danger); font-size: 14px; min-height: 18px; }

/* Thanh cuon gon gang */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 4px; }