.app {
  display: flex;
  flex-direction: column;
  min-height: 100dvh;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: var(--z-elevated);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-5);
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding-top: max(var(--space-4), env(safe-area-inset-top));
}

.app-header__title {
  font-size: var(--fs-md);
  font-weight: var(--fw-semibold);
  letter-spacing: -0.01em;
}

.app-main {
  flex: 1;
  padding: var(--space-5);
  padding-bottom: calc(var(--space-16) + env(safe-area-inset-bottom));
  max-width: 100%;
}

.app-nav {
  position: sticky;
  bottom: 0;
  z-index: var(--z-elevated);
  display: flex;
  justify-content: space-around;
  align-items: center;
  background: var(--color-bg);
  border-top: 1px solid var(--color-border);
  padding: var(--space-2) var(--space-4);
  padding-bottom: max(var(--space-2), env(safe-area-inset-bottom));
}

.app-nav__item {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: var(--tap-target);
  font-size: var(--fs-xs);
  font-weight: var(--fw-medium);
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
}

.app-nav__item--active {
  color: var(--color-primary);
}

.center-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100dvh;
  padding: var(--space-6);
  padding-top: max(var(--space-6), env(safe-area-inset-top));
  padding-bottom: max(var(--space-6), env(safe-area-inset-bottom));
}

.stack {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.stack--tight {
  gap: var(--space-2);
}

.stack--loose {
  gap: var(--space-6);
}

.row {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.row--between {
  justify-content: space-between;
}

.container {
  width: 100%;
  max-width: 480px;
  margin: 0 auto;
}

@media (min-width: 768px) {
  .app-main {
    max-width: 720px;
    margin: 0 auto;
    padding: var(--space-8);
  }
  .container {
    max-width: 560px;
  }
}

@media (min-width: 1024px) {
  .app-main {
    max-width: 960px;
  }
  .container {
    max-width: 640px;
  }
}