/* ============================================
   Layout - App Shell & Structure
   ============================================ */

.app {
  display: flex;
  flex-direction: column;
  height: 100vh;
  height: calc(var(--vh, 1vh) * 100);
  min-height: -webkit-fill-available;
  max-width: var(--app-max-width);
  margin: 0 auto;
  background: var(--bg-app);
  overflow: hidden;
  padding-top: var(--safe-top);
  padding-left: var(--safe-left);
  padding-right: var(--safe-right);
  position: relative;
}

.app-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-height: 0;
}

.chat-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100%;
  min-height: 0;
}

/* ---- Message List ---- */
.message-list {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 12px 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  background: var(--bg-chat);
  scroll-behavior: smooth;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain;
}

.message-list::-webkit-scrollbar {
  width: 0;
  background: transparent;
}

/* ---- Input Area ---- */
.input-container {
  border-top: 1px solid var(--color-gray-200);
  padding: 8px 10px;
  background: var(--bg-input);
  position: sticky;
  bottom: 0;
  z-index: var(--z-sticky);
  display: flex;
  align-items: center;
  padding-bottom: calc(8px + var(--safe-bottom));
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
}

/* ---- Loading States ---- */
.loading {
  text-align: center;
  color: var(--color-gray-500);
  padding: 48px 32px;
  font-size: 15px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.loading-spinner {
  font-size: 24px;
  animation: spin 1s linear infinite;
}

.empty-state {
  text-align: center;
  color: var(--color-gray-500);
  padding: 48px 32px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.empty-icon {
  font-size: 48px;
  opacity: 0.4;
}

.empty-state p {
  font-size: 14px;
  color: var(--color-gray-500);
  margin: 0;
}

/* ---- Animations ---- */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes messageSlideIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

@keyframes shimmer {
  0% { background-position: -200px 0; }
  100% { background-position: calc(200px + 100%) 0; }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(100%); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-20px); }
  to { opacity: 1; transform: translateY(0); }
}

.fade-in {
  animation: fadeIn 200ms ease-out;
}

.shimmer {
  background: linear-gradient(90deg, var(--color-gray-100) 25%, var(--color-gray-200) 50%, var(--color-gray-100) 75%);
  background-size: 200px 100%;
  animation: shimmer 1.5s infinite;
}