html, body {
  height: 100%;
  margin: 0;
  padding: 0;
}

body, .main-container {
  width: 100vw;
  height: 100vh;
  background: #000;
  display: flex;
  flex-direction: column;
  justify-content: stretch;
  align-items: center;
}

.main-container {
  position: relative;
  flex: 1;
  width: 100vw;
  height: 100vh;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
}

video {
  width: 100vw;
  height: 100vh;
  object-fit: contain;
  background: #000;
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 1;
}

.button-bar {
  width: 100vw;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 24px;
  background: rgba(0,0,0,0.50);
  padding: 16px 0 32px 0;
  position: absolute;
  bottom: 0;
  left: 0;
  z-index: 3; /* 保证按钮在controls下方 */
  pointer-events: auto;
}

button, #download-btn {
  padding: 12px 28px;
  font-size: 20px;
  background: #007bff;
  color: #fff;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: background .2s;
  text-decoration: none;
}

button:hover, #download-btn:hover {
  background: #0056b3;
}

#msg {
  position: absolute;
  top: 24px;
  left: 50%;
  transform: translateX(-50%);
  color: #fff;
  font-size: 18px;
  z-index: 4;
  text-shadow: 0 1px 4px #000;
}

@media (max-width: 600px) {
  button, #download-btn {
    font-size: 16px;
    padding: 10px 18px;
  }
  #msg {
    font-size: 15px;
  }
  .button-bar {
    gap: 14px;
    padding: 10px 0 16px 0;
  }
}