* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  font-family: 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.device {
  border: 3px solid var(--border);
  border-radius: 24px;
  width: 320px;
  background: var(--device-bg);
  box-shadow: 0 0 20px rgba(0,0,0,0.3);
  overflow: hidden;
}
.status-bar {
  background: var(--status-bg);
  color: var(--status-text);
  padding: 8px 12px;
  font-size: 0.85rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border);
}
.screen {
  padding: 20px;
}
#display {
  width: 100%;
  font-size: 1.8rem;
  text-align: right;
  padding: 10px;
  margin-bottom: 15px;
  background: var(--input-bg);
  border: 2px solid var(--border);
  border-radius: 8px;
  color: var(--text);
}
.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}
button {
  padding: 16px;
  font-size: 1.2rem;
  border: none;
  border-radius: 12px;
  background: var(--button-bg);
  color: var(--text);
  transition: 0.2s;
}
button:hover {
  background: var(--button-hover);
}
button.clear {
  grid-column: span 4;
  background: crimson;
  color: white;
}
.version-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 20px;
}
.version-links a {
  padding: 10px;
  border-radius: 8px;
  text-decoration: none;
  background: var(--button-bg);
  color: var(--text);
  text-align: center;
  transition: 0.2s;
}
.version-links a:hover {
  background: var(--button-hover);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121212;
    --text: #f0f0f0;
    --border: #444;
    --device-bg: #1e1e1e;
    --status-bg: #2a2a2a;
    --status-text: #aaa;
    --input-bg: #2e2e2e;
    --button-bg: #333;
    --button-hover: #555;
  }
}
@media (prefers-color-scheme: light) {
  :root {
    --bg: #f7f7f7;
    --text: #222;
    --border: #ccc;
    --device-bg: #fff;
    --status-bg: #eee;
    --status-text: #555;
    --input-bg: #fff;
    --button-bg: #ddd;
    --button-hover: #bbb;
  }
}