* { box-sizing: border-box; font-family: "Segoe UI", Arial, sans-serif; }
body { margin: 0; background: #f1f5f9; color: #0f172a; }
header { background: #0f172a; color: #fff; padding: 16px 20px; display: flex; justify-content: space-between; align-items: center; }
header h1 { margin: 0; font-size: 21px; }
#dongho { font-size: 20px; font-weight: 600; }
main { max-width: 720px; margin: 18px auto; padding: 0 14px; display: grid; gap: 16px; }
.the { background: #fff; border-radius: 14px; padding: 18px; box-shadow: 0 2px 10px rgba(0,0,0,.06); }
h2 { margin: 0 0 12px; font-size: 18px; }
label { display: block; font-size: 14px; color: #475569; margin: 10px 0 4px; }
input, select { width: 100%; padding: 13px; font-size: 17px; border: 1px solid #cbd5e1; border-radius: 10px; }
.hang { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 12px; }
.hang > * { flex: 1; min-width: 120px; }
button { padding: 14px 18px; font-size: 17px; border: 0; border-radius: 10px; cursor: pointer; color: #fff; font-weight: 700; background: #334155; }
button:disabled { opacity: .5; }
.vao { background: #16a34a; } .ra { background: #dc2626; }
.bao { margin-top: 12px; padding: 12px; border-radius: 10px; font-weight: 600; display: none; }
.bao.ok { display: block; background: #dcfce7; color: #166534; }
.bao.loi { display: block; background: #fee2e2; color: #991b1b; }
table { width: 100%; border-collapse: collapse; font-size: 15px; }
th, td { padding: 9px 8px; border-bottom: 1px solid #e2e8f0; text-align: left; }
th { background: #f8fafc; }
.nho { font-size: 13px; color: #64748b; }