@import url('https://fonts.cdnfonts.com/css/sf-pro-display');

:root {
  /* Font Family (Apple SF Pro Display / Helvetica, No System Fonts) */
  --font-family: 'SF Pro Display', 'SF Pro Text', 'Helvetica Neue', Helvetica, Arial, sans-serif;

  /* Font Sizes: 13, 16, 20, 25, 32 */
  --fs-13: 13px;
  --fs-16: 16px;
  --fs-20: 20px;
  --fs-25: 25px;
  --fs-32: 32px;

  /* Font Weights: 400 and 600 only */
  --fw-400: 400;
  --fw-600: 600;

  /* Line Heights: 1.1 for headings, 1.5 for body */
  --lh-heading: 1.1;
  --lh-body: 1.5;

  /* Concentric Radii */
  --radius-4: 4px;
  --radius-8: 8px;
  --radius-12: 12px;
  --radius-16: 16px;
  --radius-full: 1024px;

  /* Color Palette */
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-subtle: #f1f5f9;
  --border-color: #e2e8f0;
  --border-focus: #cbd5e1;
  --text-main: #0f172a;
  --text-muted: #64748b;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-subtle: #eff6ff;
  --primary-border: #dbeafe;
  --danger: #ef4444;
  --danger-bg: #fef2f2;
  --danger-border: #fee2e2;
  --online: #10b981;
}

/* Stable scrollbar prevents layout shift */
html {
  scrollbar-gutter: stable;
  overflow-y: scroll;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-page);
  color: var(--text-main);
  font-size: var(--fs-16);
  line-height: var(--lh-body);
  font-weight: var(--fw-400);
  -webkit-font-smoothing: antialiased;
}

input, textarea, button, select {
  font-family: var(--font-family);
}

/* CSS View Transitions */
@view-transition {
  navigation: auto;
}
::view-transition-old(root) {
  animation: 0.16s ease-out both fade-out;
}
::view-transition-new(root) {
  animation: 0.16s ease-in both fade-in;
}
@keyframes fade-out { from { opacity: 1; } to { opacity: 0; } }
@keyframes fade-in { from { opacity: 0; } to { opacity: 1; } }

/* ==========================================================
   Typography Rules:
   - Line height: 1.1 for headings, 1.5 for body
   - Letter spacing: >= 24px is -2%, <= 15px is +5%
   - Applicable ONLY to text and labels
   ========================================================== */
p, label, .text-content {
  line-height: var(--lh-body);
}

h1, h2, h3, h4, h5, h6, .heading {
  line-height: var(--lh-heading);
}

.fs-13:not(button):not(a):not(.btn):not(.nav-btn):not([onclick]) {
  font-size: var(--fs-13);
  line-height: var(--lh-body);
  letter-spacing: 0.05em;
}
.fs-16:not(button):not(a):not(.btn):not(.nav-btn):not([onclick]) {
  font-size: var(--fs-16);
  line-height: var(--lh-body);
  letter-spacing: normal;
}
.fs-20:not(button):not(a):not(.btn):not(.nav-btn):not([onclick]) {
  font-size: var(--fs-20);
  line-height: var(--lh-heading);
  letter-spacing: normal;
  font-weight: var(--fw-600);
}
.fs-25:not(button):not(a):not(.btn):not(.nav-btn):not([onclick]) {
  font-size: var(--fs-25);
  line-height: var(--lh-heading);
  letter-spacing: -0.02em;
  font-weight: var(--fw-600);
}
.fs-32:not(button):not(a):not(.btn):not(.nav-btn):not([onclick]) {
  font-size: var(--fs-32);
  line-height: var(--lh-heading);
  letter-spacing: -0.02em;
  font-weight: var(--fw-600);
}

.fw-400 { font-weight: var(--fw-400) !important; }
.fw-600 { font-weight: var(--fw-600) !important; }

/* ==========================================================
   CLICKABLE ELEMENTS RULE:
   All clickable elements IGNORE line spacing and letter spacing.
   ========================================================== */
button,
a,
.btn,
.btn *,
.nav-btn,
.nav-btn *,
.auth-tab-btn,
.auth-tab-btn *,
.post-action-btn,
.post-action-btn *,
.convo-item,
.convo-item *,
[role="button"],
[onclick],
[onclick] *,
input[type="button"],
input[type="submit"] {
  letter-spacing: normal !important;
  line-height: 1.2 !important;
}

/* Tab Management */
.tab-pane {
  display: none !important;
  flex-direction: column;
  gap: 16px;
}
.tab-pane.active {
  display: flex !important;
}

/* Avatars & Concentric Online Indicator */
.avatar-48 { width: 48px; height: 48px; border-radius: var(--radius-full); object-fit: cover; display: block; flex-shrink: 0; }
.avatar-32 { width: 32px; height: 32px; border-radius: var(--radius-full); object-fit: cover; display: block; flex-shrink: 0; }
.avatar-24 { width: 24px; height: 24px; border-radius: var(--radius-full); object-fit: cover; display: block; flex-shrink: 0; }

.avatar-online {
  box-shadow: 0 0 0 2px var(--bg-card), 0 0 0 4px var(--online);
}

/* Header */
.header-bar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  height: 64px;
  display: flex;
  align-items: center;
  padding: 0 24px;
}
.header-inner {
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand-link {
  text-decoration: none;
  color: var(--text-main);
  display: flex;
  align-items: baseline;
  gap: 6px;
}

/* Layout */
.main-layout {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px 16px;
  display: flex;
  gap: 20px;
}
.sidebar {
  width: 240px;
  min-width: 240px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.sidebar-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-16);
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.content-area {
  flex: 1;
  min-width: 0;
}

/* Uniform Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-16);
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* Sidebar Nav Buttons */
.nav-btn {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  border-radius: var(--radius-8);
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  font-size: var(--fs-16);
  font-weight: var(--fw-600);
  cursor: pointer;
  text-align: left;
  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}
.nav-btn:hover {
  background-color: var(--bg-subtle);
  border-color: var(--border-color);
  color: var(--text-main);
}
.nav-btn.active {
  background-color: var(--primary-subtle);
  border-color: var(--primary-border);
  color: var(--primary);
}

/* Form Inputs */
.input-field {
  width: 100%;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-8);
  padding: 10px 14px;
  font-size: var(--fs-16);
  background-color: var(--bg-subtle);
  color: var(--text-main);
  outline: none;
  transition: border-color 0.15s ease, background-color 0.15s ease, box-shadow 0.15s ease;
}
.input-field:hover {
  border-color: var(--border-focus);
  background-color: #ffffff;
}
.input-field:focus {
  border-color: var(--primary);
  background-color: #ffffff;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

/* Equal Segmented Auth Tabs */
.auth-tab-control {
  display: flex;
  background-color: var(--bg-subtle);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-8);
  padding: 4px;
  gap: 4px;
}
.auth-tab-btn {
  flex: 1;
  height: 32px;
  border-radius: var(--radius-4);
  border: 1px solid transparent;
  background: transparent;
  color: var(--text-muted);
  font-size: var(--fs-13);
  font-weight: var(--fw-600);
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.auth-tab-btn:hover {
  color: var(--text-main);
}
.auth-tab-btn.active {
  background-color: var(--bg-card);
  border-color: var(--border-color);
  color: var(--primary);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.04);
}

/* Standardized Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 36px;
  padding: 0 16px;
  border-radius: var(--radius-8);
  font-size: var(--fs-13);
  font-weight: var(--fw-600);
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background-color: var(--primary);
  border-color: var(--primary);
  color: #ffffff;
}
.btn-primary:hover {
  background-color: var(--primary-hover);
  border-color: var(--primary-hover);
}

.btn-secondary {
  background-color: var(--bg-card);
  border-color: var(--border-color);
  color: var(--text-muted);
}
.btn-secondary:hover {
  background-color: var(--bg-subtle);
  border-color: var(--border-focus);
  color: var(--text-main);
}

.btn-danger {
  background-color: var(--danger-bg);
  border-color: var(--danger-border);
  color: var(--danger);
}
.btn-danger:hover {
  background-color: #fee2e2;
  border-color: #fca5a5;
}

.btn-view {
  background-color: var(--primary-subtle);
  border-color: var(--primary-border);
  color: var(--primary);
}
.btn-view:hover {
  background-color: #dbeafe;
  border-color: #bfdbfe;
}

/* Dynamic CSS Spinners */
.spinner {
  display: inline-block;
  width: 14px;
  height: 14px;
  border: 2px solid rgba(255, 255, 255, 0.35);
  border-top-color: #ffffff;
  border-radius: var(--radius-full);
  animation: spin 0.6s linear infinite;
  vertical-align: middle;
  flex-shrink: 0;
  box-sizing: border-box;
}

.spinner-dark {
  border-color: rgba(15, 23, 42, 0.2);
  border-top-color: var(--primary);
}

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

/* Loading Spinner Container for Sections */
.loading-spinner-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
  gap: 12px;
  color: var(--text-muted);
}

/* Messages Pane */
.messages-container {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-16);
  height: 650px;
  display: flex;
  overflow: hidden;
}
.convos-pane {
  width: 320px;
  min-width: 320px;
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
}
.chat-pane {
  flex: 1;
  display: flex;
  flex-direction: column;
  background: var(--bg-page);
}
.chat-header {
  height: 64px;
  padding: 0 20px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  gap: 12px;
}
.chat-stream {
  flex: 1;
  padding: 20px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.chat-bubble {
  max-width: 70%;
  padding: 10px 16px;
  border-radius: var(--radius-12);
  font-size: var(--fs-16);
  word-break: break-word;
}
.chat-bubble.mine {
  background: var(--primary);
  color: #ffffff;
  align-self: flex-end;
}
.chat-bubble.theirs {
  background: #ffffff;
  border: 1px solid var(--border-color);
  color: var(--text-main);
  align-self: flex-start;
}
.convo-item {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
  border-left: 3px solid transparent;
  display: flex;
  gap: 12px;
  align-items: center;
  cursor: pointer;
  background: transparent;
  transition: background-color 0.15s ease, border-color 0.15s ease;
}
.convo-item:hover {
  background-color: var(--bg-subtle);
}
.convo-item.active {
  background-color: var(--primary-subtle);
  border-left-color: var(--primary);
}

/* Skeletons */
.skeleton {
  background: linear-gradient(90deg, #f1f5f9 25%, #e2e8f0 50%, #f1f5f9 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite ease-in-out;
  border-radius: var(--radius-4);
}
@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

.pulsing-dots {
  display: inline-block;
  animation: pulse 1s infinite alternate;
  letter-spacing: 2px;
}
@keyframes pulse { 0% { opacity: 0.3; } 100% { opacity: 1; } }

.toast-slide-in {
  animation: toastIn 0.25s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}
@keyframes toastIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 768px) {
  .main-layout { flex-direction: column; }
  .sidebar { width: 100%; min-width: 100%; }
  .messages-container { flex-direction: column; height: 750px; }
  .convos-pane { width: 100%; min-width: 100%; height: 260px; border-right: none; border-bottom: 1px solid var(--border-color); }
}