:root {
  --fg: #fff;
  --bg: #000;
}

body {
  margin: 0;
  font-family: "Inter", "Segoe UI", Tahoma, sans-serif;
  background: var(--bg);
  color: var(--fg);
  text-align: center;
  min-height: 100vh;
}

#space-bg {
  position: fixed;
  inset: 0;
  z-index: -1;   /* nền nằm sau cùng */
  display: block;
}

.container {
  padding: 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}

/* Tiêu đề */
h1 {
  font-size: 1.4rem;
  margin: 10px 0;
  font-weight: 600;
}

/* Nút ngân hàng */
.bank-buttons {
  display: flex;
  flex-direction: column;
  gap: 14px;
  width: 100%;
}

.classic-btn {
  background: rgba(255,255,255,.05);
  border: 1.5px solid rgba(255,255,255,.3);
  color: var(--fg);
  font-size: 1.1rem;
  padding: 14px 16px;
  border-radius: 18px;
  cursor: pointer;
  width: 100%;
  text-align: center;
  backdrop-filter: blur(4px);
  transition: all .25s ease-in-out;
}
.classic-btn:hover {
  background: rgba(255,255,255,.15);
}

/* Overlay */
.overlay {
  position: fixed;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background: rgba(0,0,0,0.9);
  display: none;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  padding: 10px;
  box-sizing: border-box;
}
.overlay img {
  max-width: 100%;
  max-height: 100%;
  border-radius: 10px;
}