:root {
  --button-bg: #0c0f14;
  --button-border: #ffffff;
  --button-text: #fffdf8;
  --button-shadow: rgba(12, 15, 20, 0.42);
}

* {
  box-sizing: border-box;
}

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

body {
  font-family: "Noto Serif SC", "Songti SC", "STSong", serif;
  background: #f7e5c6;
}

.app-landing {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.background-image {
  display: block;
  width: 100%;
  height: 100vh;
  object-fit: cover;
}

.download-btn {
  position: absolute;
  left: 50%;
  bottom: 10vh;
  transform: translateX(-50%);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 220px;
  min-height: 56px;
  padding: 14px 28px;
  border-radius: 999px;
  border: 3px solid var(--button-border);
  background: var(--button-bg);
  color: var(--button-text);
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-decoration: none;
  box-shadow:
    0 16px 30px var(--button-shadow),
    0 0 0 8px rgba(255, 255, 255, 0.16);
  animation: download-shake 1.9s ease-in-out infinite;
}

.download-btn:hover {
  animation-play-state: paused;
}

@keyframes download-shake {
  0%,
  100% {
    transform: translateX(-50%) rotate(0deg);
  }

  8% {
    transform: translateX(-50%) rotate(-2deg);
  }

  16% {
    transform: translateX(-50%) rotate(2deg);
  }

  24% {
    transform: translateX(-50%) rotate(-1.5deg);
  }

  32% {
    transform: translateX(-50%) rotate(1.5deg);
  }

  40% {
    transform: translateX(-50%) rotate(0deg);
  }
}

@media (max-width: 640px) {
  .download-btn {
    bottom: 7vh;
    min-width: 188px;
    min-height: 50px;
    padding: 12px 22px;
    font-size: 0.95rem;
  }
}