/* Shell: version toggle only */
:root {
  --shell-bg: #1a5f7a;
  --shell-active: #fff;
  --shell-inactive: rgba(255, 255, 255, 0.7);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: system-ui, -apple-system, sans-serif;
}

.shell-header {
  flex: 0 0 auto;
  background: var(--shell-bg);
  padding: 0.5rem 1rem;
  display: flex;
  justify-content: center;
  align-items: center;
}

.shell-toggle {
  display: flex;
  gap: 0;
  border-radius: 8px;
  overflow: hidden;
  background: rgba(0, 0, 0, 0.2);
}

.shell-btn {
  padding: 0.5rem 1.25rem;
  border: none;
  background: transparent;
  color: var(--shell-inactive);
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 500;
  transition: background 0.2s, color 0.2s;
}

.shell-btn:hover {
  color: var(--shell-active);
}

.shell-btn.active {
  background: var(--shell-active);
  color: var(--shell-bg);
}

.shell-main {
  flex: 1;
  position: relative;
  min-height: 0;
}

.shell-frame {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.shell-frame.hidden {
  display: none;
}