/* ==================== LESSON PAGE STYLING ==================== */

/* Hero banner */
.lesson-hero {
  position: relative;
  min-height: 320px;
  border-radius: 24px;
  overflow: hidden;
  margin-bottom: 2rem;
  background-size: cover;
  background-position: center;
  display: flex;
  align-items: flex-end;
}

.lesson-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(30,20,60,0.85), rgba(6,182,212,0.55));
  z-index: 1;
}

.lesson-hero-content {
  position: relative;
  z-index: 2;
  padding: 2.5rem 2rem;
  width: 100%;
  color: #fff;
}

.lesson-hero-badges {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1rem;
}

.lesson-badge {
  background: rgba(255,255,255,0.15);
  backdrop-filter: blur(8px);
  border: 1px solid rgba(255,255,255,0.2);
  padding: 0.35rem 0.85rem;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.lesson-badge.xp { color: #fbbf24; border-color: rgba(251,191,36,0.4); }
.lesson-badge.time { color: #06b6d4; border-color: rgba(6,182,212,0.4); }

.lesson-hero h1 {
  font-size: 2rem;
  font-weight: 900;
  margin: 0.5rem 0 0.75rem;
  line-height: 1.15;
}

.lesson-hero p {
  color: rgba(255,255,255,0.85);
  font-size: 1rem;
  margin: 0;
  max-width: 700px;
  line-height: 1.6;
}

@media (min-width: 768px) {
  .lesson-hero { min-height: 380px; }
  .lesson-hero h1 { font-size: 2.75rem; }
  .lesson-hero-content { padding: 3rem; }
}

/* Reading progress bar (top of page, sticky) */
.lesson-progress-bar {
  position: sticky;
  top: 0;
  height: 3px;
  background: rgba(255,255,255,0.08);
  z-index: 40;
  margin: -1rem 0 2rem;
  border-radius: 3px;
  overflow: hidden;
}

.lesson-progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, #a855f7, #06b6d4);
  transition: width 0.2s;
}

/* Table of contents */
.lesson-toc {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 20px;
  padding: 1.5rem;
  margin-bottom: 2rem;
}

.lesson-toc h3 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 2px;
  color: #9ca3af;
  margin: 0 0 1rem;
  font-weight: 700;
}

.lesson-toc ol {
  list-style: none;
  padding: 0;
  margin: 0;
  counter-reset: toc;
}

.lesson-toc li {
  counter-increment: toc;
  padding: 0.4rem 0;
  border-bottom: 1px solid rgba(255,255,255,0.04);
}

.lesson-toc li:last-child { border-bottom: none; }

.lesson-toc li::before {
  content: counter(toc) ".";
  color: #a855f7;
  font-weight: 800;
  margin-right: 0.75rem;
  display: inline-block;
  width: 1.5rem;
}

.lesson-toc a {
  color: #d1d5db;
  text-decoration: none;
  transition: color 0.2s;
}

.lesson-toc a:hover { color: #06b6d4; }

/* Lesson body — prose */
.lesson-body {
  font-size: 1rem;
  line-height: 1.75;
  color: #d1d5db;
}

.lesson-body h2 {
  font-size: 1.75rem;
  font-weight: 900;
  color: #fff;
  margin: 3rem 0 1rem;
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid rgba(168,85,247,0.2);
}

.lesson-body h2 .lesson-num {
  color: #a855f7;
  font-size: 2.25rem;
  font-weight: 900;
  line-height: 1;
}

.lesson-body h3 {
  font-size: 1.25rem;
  font-weight: 800;
  color: #fff;
  margin: 2rem 0 0.75rem;
}

.lesson-body p {
  margin: 0 0 1.25rem;
}

.lesson-body strong { color: #fff; font-weight: 700; }
.lesson-body em { color: #06b6d4; font-style: normal; font-weight: 600; }

.lesson-body ul, .lesson-body ol {
  margin: 0 0 1.5rem;
  padding-left: 1.5rem;
}

.lesson-body li {
  margin-bottom: 0.5rem;
}

/* Callouts */
.lesson-callout {
  padding: 1.25rem 1.5rem;
  border-radius: 16px;
  margin: 1.5rem 0;
  border-left: 4px solid;
  display: flex;
  gap: 1rem;
  align-items: flex-start;
}

.lesson-callout .icon { font-size: 1.5rem; flex-shrink: 0; }
.lesson-callout .content { flex: 1; }
.lesson-callout .title { font-weight: 800; margin-bottom: 0.5rem; color: #fff; }

.lesson-callout.info {
  background: rgba(6,182,212,0.08);
  border-color: #06b6d4;
}

.lesson-callout.warn {
  background: rgba(245,158,11,0.08);
  border-color: #f59e0b;
}

.lesson-callout.success {
  background: rgba(34,197,94,0.08);
  border-color: #22c55e;
}

/* Diagram grids (like the 4-step diagram) */
.lesson-diagram {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 0.75rem;
  margin: 1.5rem 0;
}

.lesson-diagram-card {
  background: linear-gradient(135deg, rgba(168,85,247,0.12), rgba(6,182,212,0.12));
  border: 1px solid rgba(168,85,247,0.35);
  border-radius: 16px;
  padding: 1rem;
  text-align: center;
}

.lesson-diagram-card .icon { font-size: 2rem; margin-bottom: 0.5rem; }
.lesson-diagram-card .label {
  font-weight: 900;
  color: #a855f7;
  font-size: 0.85rem;
  letter-spacing: 1px;
  text-transform: uppercase;
}
.lesson-diagram-card .desc {
  font-size: 0.75rem;
  color: #9ca3af;
  margin-top: 0.25rem;
}

/* Comparison tables */
.lesson-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  background: rgba(255,255,255,0.02);
  border-radius: 16px;
  overflow: hidden;
  font-size: 0.9rem;
}

.lesson-table th {
  background: linear-gradient(135deg, rgba(168,85,247,0.25), rgba(6,182,212,0.25));
  color: #fff;
  font-weight: 800;
  padding: 0.85rem 1rem;
  text-align: left;
  text-transform: uppercase;
  letter-spacing: 1px;
  font-size: 0.75rem;
}

.lesson-table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid rgba(255,255,255,0.06);
  color: #d1d5db;
}

.lesson-table tr:nth-child(even) { background: rgba(255,255,255,0.02); }
.lesson-table tr:last-child td { border-bottom: none; }
.lesson-table tr:hover { background: rgba(168,85,247,0.08); }

/* Images inline */
.lesson-image {
  margin: 2rem 0;
  border-radius: 20px;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,0.08);
}

.lesson-image img {
  width: 100%;
  height: auto;
  display: block;
}

.lesson-image figcaption {
  padding: 0.75rem 1rem;
  background: rgba(255,255,255,0.03);
  font-size: 0.85rem;
  color: #9ca3af;
  font-style: italic;
}

/* Key terms glossary */
.lesson-glossary {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 2px solid rgba(168,85,247,0.2);
}

.lesson-glossary h2 {
  font-size: 1.75rem;
  font-weight: 900;
  color: #fff;
  margin: 0 0 1.5rem;
}

.lesson-glossary-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 768px) {
  .lesson-glossary-grid { grid-template-columns: repeat(2, 1fr); }
}

.lesson-term {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 14px;
  padding: 1rem 1.25rem;
}

.lesson-term .term {
  font-weight: 800;
  color: #a855f7;
  text-transform: uppercase;
  letter-spacing: 1px;
  font-size: 0.8rem;
  margin-bottom: 0.35rem;
}

.lesson-term .definition {
  font-size: 0.9rem;
  color: #d1d5db;
  line-height: 1.5;
}

/* Sticky TOC on desktop */
@media (min-width: 1024px) {
  .lesson-layout {
    display: grid;
    grid-template-columns: 240px 1fr;
    gap: 2rem;
    align-items: start;
  }
  .lesson-toc { position: sticky; top: 1rem; max-height: calc(100vh - 2rem); overflow-y: auto; }
}

/* Reading time label */
.lesson-reading-time {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: #06b6d4;
  margin-bottom: 1rem;
  font-weight: 600;
}

/* Key takeaways special block */
.lesson-takeaways {
  background: linear-gradient(135deg, rgba(34,197,94,0.08), rgba(6,182,212,0.08));
  border: 1px solid rgba(34,197,94,0.3);
  border-radius: 20px;
  padding: 1.5rem;
  margin: 2rem 0;
}

.lesson-takeaways h2 {
  border-bottom: none;
  margin-top: 0;
  color: #22c55e;
}


/* ==================== LESSON DRAWER ==================== */

.lesson-drawer-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(6px);
  z-index: 9998;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}

.lesson-drawer-backdrop.active {
  opacity: 1;
  pointer-events: auto;
}

.lesson-drawer {
  position: fixed;
  top: 0;
  right: 0;
  height: 100vh;
  width: 100%;
  max-width: 780px;
  background: linear-gradient(160deg, rgba(20, 15, 40, 0.99), rgba(10, 10, 25, 0.99));
  border-left: 1px solid rgba(168, 85, 247, 0.25);
  z-index: 9999;
  transform: translateX(100%);
  transition: transform 0.35s cubic-bezier(0.32, 0.72, 0, 1);
  display: flex;
  flex-direction: column;
  box-shadow: -30px 0 80px rgba(0, 0, 0, 0.5);
}

.lesson-drawer-backdrop.active + .lesson-drawer,
.lesson-drawer.active {
  transform: translateX(0);
}

.lesson-drawer-header {
  position: sticky;
  top: 0;
  background: linear-gradient(180deg, rgba(20, 15, 40, 0.98), rgba(20, 15, 40, 0.92));
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(168, 85, 247, 0.2);
  padding: 1rem 1.5rem;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.lesson-drawer-header h2 {
  font-size: 1.1rem;
  font-weight: 900;
  color: #fff;
  margin: 0;
  flex: 1;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lesson-drawer-close {
  width: 40px;
  height: 40px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.1);
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  flex-shrink: 0;
  font-size: 1.1rem;
}

.lesson-drawer-close:hover {
  background: rgba(239, 68, 68, 0.2);
  border-color: rgba(239, 68, 68, 0.5);
}

.lesson-drawer-progress {
  height: 3px;
  background: rgba(255, 255, 255, 0.08);
  position: relative;
  overflow: hidden;
  flex-shrink: 0;
}

.lesson-drawer-progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, #a855f7, #06b6d4);
  transition: width 0.15s ease;
}

.lesson-drawer-body {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem;
  scroll-behavior: smooth;
}

.lesson-drawer-body::-webkit-scrollbar { width: 8px; }
.lesson-drawer-body::-webkit-scrollbar-track { background: rgba(255, 255, 255, 0.03); }
.lesson-drawer-body::-webkit-scrollbar-thumb {
  background: rgba(168, 85, 247, 0.4);
  border-radius: 4px;
}
.lesson-drawer-body::-webkit-scrollbar-thumb:hover {
  background: rgba(168, 85, 247, 0.6);
}

/* TOC in drawer */
.lesson-drawer .lesson-toc {
  margin-bottom: 2rem;
}

/* Adjust layout for the drawer — no more 2-col grid */
.lesson-drawer .lesson-layout {
  display: block !important;
}

.lesson-drawer .lesson-body h2 {
  font-size: 1.4rem;
  margin: 2rem 0 0.75rem;
}

.lesson-drawer .lesson-body h2 .lesson-num {
  font-size: 1.6rem;
}

/* Mobile: drawer goes full width */
@media (max-width: 768px) {
  .lesson-drawer {
    max-width: 100%;
    border-left: none;
  }
  .lesson-drawer-header {
    padding: 0.85rem 1rem;
  }
  .lesson-drawer-header h2 {
    font-size: 0.95rem;
  }
  .lesson-drawer-body {
    padding: 1rem;
  }
}

/* ---- Open Full Lesson Button ---- */
.open-lesson-btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: 1.25rem 1.5rem;
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  border: none;
  border-radius: 20px;
  color: #fff;
  cursor: pointer;
  font-family: inherit;
  font-weight: 800;
  font-size: 1rem;
  transition: all 0.2s;
  box-shadow: 0 10px 30px rgba(168, 85, 247, 0.35);
  margin: 0;
}

.open-lesson-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 15px 40px rgba(168, 85, 247, 0.5);
}

.open-lesson-btn:active {
  transform: translateY(0);
}

.open-lesson-btn .left {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  text-align: left;
}

.open-lesson-btn .icon {
  font-size: 1.75rem;
  flex-shrink: 0;
}

.open-lesson-btn .label {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.open-lesson-btn .title {
  font-size: 1.05rem;
  font-weight: 900;
}

.open-lesson-btn .subtitle {
  font-size: 0.75rem;
  opacity: 0.85;
  font-weight: 500;
}

.open-lesson-btn .arrow {
  font-size: 1.25rem;
  flex-shrink: 0;
}

.open-lesson-btn .read-badge {
  background: rgba(34, 197, 94, 0.9);
  padding: 0.25rem 0.6rem;
  border-radius: 8px;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-left: 0.5rem;
}


/* ==================== PROF. KELVIN AI TEACHER ==================== */
.kelvin-fab {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  color: #fff;
  border: none;
  border-radius: 100px;
  padding: 1rem 1.5rem;
  font-family: inherit;
  font-weight: 800;
  font-size: 0.95rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  z-index: 9997;
  box-shadow: 0 12px 40px rgba(168,85,247,0.5);
  transition: all 0.25s;
}

.kelvin-fab:hover {
  transform: translateY(-3px) scale(1.03);
  box-shadow: 0 18px 50px rgba(168,85,247,0.7);
}

.kelvin-fab .avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: rgba(255,255,255,0.25);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
}

.kelvin-fab.hidden { display: none; }

.kelvin-panel {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: 400px;
  height: 600px;
  max-height: 85vh;
  max-width: calc(100vw - 2rem);
  background: linear-gradient(160deg, rgba(20,15,40,0.99), rgba(10,10,25,0.99));
  border: 1px solid rgba(168,85,247,0.35);
  border-radius: 24px;
  z-index: 9998;
  display: flex;
  flex-direction: column;
  box-shadow: 0 30px 80px rgba(0,0,0,0.6);
  transform: translateY(20px) scale(0.95);
  opacity: 0;
  pointer-events: none;
  transition: all 0.3s cubic-bezier(0.32, 0.72, 0, 1);
  overflow: hidden;
}

.kelvin-panel.active {
  transform: translateY(0) scale(1);
  opacity: 1;
  pointer-events: auto;
}

.kelvin-panel.minimized {
  height: auto;
}

.kelvin-panel.minimized .kelvin-body,
.kelvin-panel.minimized .kelvin-footer {
  display: none;
}

.kelvin-header {
  padding: 0.9rem 1.1rem;
  background: linear-gradient(135deg, rgba(168,85,247,0.2), rgba(6,182,212,0.2));
  border-bottom: 1px solid rgba(168,85,247,0.25);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  cursor: pointer;
}

.kelvin-header .avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  flex-shrink: 0;
}

.kelvin-header .info { flex: 1; min-width: 0; }
.kelvin-header .name { font-weight: 900; font-size: 0.95rem; color: #fff; }
.kelvin-header .sub { font-size: 0.72rem; color: rgba(255,255,255,0.6); margin-top: 1px; }

.kelvin-header .actions { display: flex; gap: 0.25rem; }

.kelvin-header .btn-icon {
  width: 30px;
  height: 30px;
  border-radius: 10px;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.1);
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  transition: all 0.15s;
  flex-shrink: 0;
}

.kelvin-header .btn-icon:hover {
  background: rgba(239,68,68,0.2);
  border-color: rgba(239,68,68,0.5);
}

.kelvin-body {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.kelvin-body::-webkit-scrollbar { width: 6px; }
.kelvin-body::-webkit-scrollbar-thumb {
  background: rgba(168,85,247,0.4);
  border-radius: 3px;
}

.kelvin-msg {
  display: flex;
  gap: 0.5rem;
  max-width: 90%;
  animation: kelvinFade 0.3s ease;
}

@keyframes kelvinFade {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.kelvin-msg.user { align-self: flex-end; flex-direction: row-reverse; }

.kelvin-msg .bubble {
  padding: 0.65rem 0.95rem;
  border-radius: 16px;
  font-size: 0.87rem;
  line-height: 1.5;
  word-wrap: break-word;
  white-space: pre-wrap;
}

.kelvin-msg.user .bubble {
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  color: #fff;
  border-bottom-right-radius: 4px;
}

.kelvin-msg.ai .bubble {
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.08);
  color: #e5e7eb;
  border-bottom-left-radius: 4px;
}

.kelvin-msg .bubble strong { color: #06b6d4; font-weight: 700; }

.kelvin-msg .avatar-sm {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  flex-shrink: 0;
  align-self: flex-end;
}

.kelvin-typing {
  display: flex;
  gap: 4px;
  padding: 0.65rem 1rem;
  background: rgba(255,255,255,0.06);
  border-radius: 16px;
  width: fit-content;
}

.kelvin-typing .dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #a855f7;
  animation: kelvinDot 1.4s infinite;
}

.kelvin-typing .dot:nth-child(2) { animation-delay: 0.2s; }
.kelvin-typing .dot:nth-child(3) { animation-delay: 0.4s; }

@keyframes kelvinDot {
  0%, 60%, 100% { opacity: 0.3; transform: scale(0.8); }
  30% { opacity: 1; transform: scale(1.1); }
}

.kelvin-quick {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0.5rem 0;
}

.kelvin-quick button {
  background: rgba(168,85,247,0.12);
  border: 1px solid rgba(168,85,247,0.35);
  color: #e5e7eb;
  font-family: inherit;
  font-size: 0.75rem;
  padding: 0.4rem 0.75rem;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.15s;
}

.kelvin-quick button:hover {
  background: rgba(168,85,247,0.25);
  border-color: #a855f7;
}

.kelvin-footer {
  padding: 0.75rem 1rem;
  border-top: 1px solid rgba(168,85,247,0.2);
  background: rgba(0,0,0,0.2);
}

.kelvin-input-row {
  display: flex;
  gap: 0.5rem;
  align-items: flex-end;
}

.kelvin-input {
  flex: 1;
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 20px;
  padding: 0.65rem 1rem;
  color: #fff;
  font-family: inherit;
  font-size: 0.87rem;
  resize: none;
  max-height: 100px;
  min-height: 40px;
  transition: all 0.15s;
}

.kelvin-input:focus {
  outline: none;
  border-color: #a855f7;
  background: rgba(168,85,247,0.08);
}

.kelvin-send {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, #a855f7, #06b6d4);
  border: none;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s;
  flex-shrink: 0;
  font-size: 1rem;
}

.kelvin-send:hover { transform: scale(1.08); }
.kelvin-send:disabled { opacity: 0.5; cursor: not-allowed; }

@media (max-width: 480px) {
  .kelvin-panel {
    bottom: 0;
    right: 0;
    width: 100vw;
    height: 100vh;
    max-height: 100vh;
    max-width: 100vw;
    border-radius: 0;
    border: none;
  }
  .kelvin-fab { bottom: 1rem; right: 1rem; padding: 0.85rem 1.15rem; font-size: 0.85rem; }
}