/* ========================================
   Exam Prep - Astra AI Dark Theme
   Uses variables.css (--bg-*, --text-*, --accent, --brand-primary, etc.)
======================================== */

/* ========================================
   Exam Prep Keyframes
======================================== */
@keyframes ep-fadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to   { opacity: 1; transform: translateY(0); }
}

@keyframes ep-slideInRight {
    from { opacity: 0; transform: translateX(30px); }
    to   { opacity: 1; transform: translateX(0); }
}

@keyframes ep-scaleIn {
    from { opacity: 0; transform: scale(0.9); }
    to   { opacity: 1; transform: scale(1); }
}

@keyframes ep-nodeGlow {
    0%, 100% { box-shadow: 0 0 20px var(--brand-primary-glow); }
    50%      { box-shadow: 0 0 30px var(--brand-primary-glow), 0 0 60px rgba(245, 184, 0, 0.1); }
}

@keyframes ep-msgSlideIn {
    from { opacity: 0; transform: translateY(12px) scale(0.97); }
    to   { opacity: 1; transform: translateY(0) scale(1); }
}

@keyframes ep-wizardStep {
    from { opacity: 0; transform: translateX(24px); }
    to   { opacity: 1; transform: translateX(0); }
}

@keyframes ep-chipFloat {
    from { opacity: 0; transform: translateY(8px) scale(0.95); }
    to   { opacity: 1; transform: translateY(0) scale(1); }
}

/* ========================================
   1. SIDEBAR (.app-sidebar)
======================================== */
.app-sidebar {
    width: 236px;
    flex-shrink: 0;
    display: flex;
    flex-direction: column;
    padding: var(--space-4);
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.02), transparent 18%),
        var(--bg-glass);
    border-right: 1px solid var(--border-default);
    box-shadow: inset -1px 0 0 rgba(255, 255, 255, 0.02);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    transition: width var(--transition-base), padding var(--transition-base), background var(--transition-base);
    z-index: 100;
}

[data-theme="dark"] .app-sidebar {
    background:
        linear-gradient(180deg, rgba(245, 184, 0, 0.04), transparent 16%),
        var(--bg-glass);
    border-right-color: var(--border-default);
}

.sidebar-brand {
    padding: var(--space-3);
    font-size: 12px;
    font-weight: 800;
    color: var(--brand-primary);
    text-transform: uppercase;
    letter-spacing: 0.7px;
    line-height: 1.2;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: var(--space-2);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-xl);
    background: rgba(255, 255, 255, 0.02);
    margin-bottom: var(--space-3);
}

/* Sidebar toggle button */
.sidebar-toggle-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    border-radius: var(--radius-md);
    background: var(--bg-hover);
    color: var(--text-secondary);
    border: none;
    cursor: pointer;
    transition: var(--transition-spring);
    flex-shrink: 0;
    margin-left: auto;
}

.sidebar-toggle-btn:hover {
    background: var(--bg-active);
    color: var(--text-primary);
    transform: translateX(-1px);
}

.sidebar-toggle-btn svg {
    width: 15px;
    height: 15px;
    transition: transform 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

/* ========================================
   Sidebar Collapsed State
======================================== */
.app-sidebar.collapsed {
    width: 88px;
}

.app-sidebar.collapsed .sidebar-brand {
    justify-content: center;
    padding: var(--space-3);
}

.app-sidebar.collapsed .sidebar-brand-text {
    display: none;
}

.app-sidebar.collapsed .sidebar-toggle-btn {
    margin-left: 0;
}

.app-sidebar.collapsed .sidebar-toggle-btn svg {
    transform: rotate(180deg);
}

.app-sidebar.collapsed .sidebar-item span {
    display: none;
}

.app-sidebar.collapsed .sidebar-item {
    justify-content: center;
    padding: var(--space-3);
}

.app-sidebar.collapsed .sidebar-nav,
.app-sidebar.collapsed .sidebar-bottom {
    padding: var(--space-2);
}

.app-sidebar.collapsed .sidebar-upgrade {
    padding: var(--space-2);
}

.app-sidebar.collapsed .sidebar-upgrade-text {
    display: none;
}

.app-sidebar.collapsed .sidebar-upgrade-btn {
    justify-content: center;
    padding: var(--space-3);
}

/* Hide toggle on bottom-tab-bar layout */
@media (max-width: 480px) {
    .sidebar-toggle-btn {
        display: none;
    }
}

.sidebar-nav {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    padding: 0;
}

.sidebar-item {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: 14px var(--space-4);
    border-radius: var(--radius-lg);
    background: transparent;
    border: 1px solid transparent;
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    transition: all 0.28s cubic-bezier(0.22, 1, 0.36, 1);
    width: 100%;
    text-align: left;
    position: relative;
    overflow: hidden;
}

.sidebar-item:hover {
    background: var(--bg-hover);
    border-color: var(--border-subtle);
    color: var(--text-primary);
    transform: translateX(3px);
}

.sidebar-item:active {
    transform: scale(0.97);
    transition-duration: 0.1s;
}

.sidebar-item.active {
    background: linear-gradient(135deg, rgba(245, 184, 0, 0.16), rgba(245, 184, 0, 0.08));
    border-color: rgba(245, 184, 0, 0.22);
    color: var(--accent);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.05), 0 10px 28px rgba(245, 184, 0, 0.08);
}

.sidebar-item svg {
    width: 20px;
    height: 20px;
    flex-shrink: 0;
    stroke: currentColor;
    opacity: 0.95;
}

/* Upgrade CTA */
.sidebar-upgrade {
    padding: var(--space-3) 0;
}

.sidebar-upgrade.hidden {
    display: none;
}

.sidebar-upgrade-btn {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    width: 100%;
    padding: 14px var(--space-4);
    background: var(--brand-gradient);
    color: var(--accent-text);
    font-size: 13px;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.22, 1, 0.36, 1);
    position: relative;
    overflow: hidden;
    text-align: left;
    box-shadow: 0 10px 28px rgba(245, 184, 0, 0.22);
}

.sidebar-upgrade-btn svg {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
    stroke: var(--accent-text);
    fill: var(--accent-text);
    opacity: 0.8;
}

.sidebar-upgrade-text {
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.sidebar-upgrade-btn::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transform: translateX(-100%);
    transition: transform 0.5s ease;
}

.sidebar-upgrade-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 16px 36px rgba(245, 184, 0, 0.3);
}

.sidebar-upgrade-btn:hover::before {
    transform: translateX(100%);
}

.sidebar-upgrade-btn:active {
    transform: scale(0.97);
    transition-duration: 0.1s;
}

.sidebar-bottom {
    padding: var(--space-3) 0 0;
    margin-top: var(--space-2);
    border-top: 1px solid var(--border-subtle);
}

[data-theme="dark"] .sidebar-bottom {
    border-top-color: var(--border-subtle);
}



/* ========================================
   3. DASHBOARD (.ep-dashboard)
======================================== */
.ep-dashboard {
    display: flex;
    flex-direction: column;
    height: 100%;
    padding: var(--space-6);
    gap: var(--space-5);
    overflow: auto;
    animation: ep-fadeInUp 0.4s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.ep-dashboard-header {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    flex-wrap: wrap;
}

.ep-search-bar {
    flex: 1;
    min-width: 200px;
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    transition: var(--transition-fast);
}

.ep-search-bar:focus-within {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px var(--accent-subtle);
}

.ep-search-bar svg {
    width: 18px;
    height: 18px;
    color: var(--text-tertiary);
    flex-shrink: 0;
}

.ep-search-bar input {
    flex: 1;
    background: transparent;
    border: none;
    font-size: 14px;
    color: var(--text-primary);
    outline: none;
}

.ep-search-bar input::placeholder {
    color: var(--text-placeholder);
}

.ep-new-exam-btn {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    background: var(--brand-primary);
    color: #000;
    font-size: 14px;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    transition: var(--transition-fast);
}

.ep-new-exam-btn:hover {
    background: var(--brand-primary-hover);
    transform: translateY(-2px) scale(1.03);
    box-shadow: var(--shadow-glow);
}

.ep-new-exam-btn:active {
    transform: scale(0.97);
    transition-duration: 0.1s;
}

.ep-new-exam-btn svg {
    width: 18px;
    height: 18px;
    stroke: currentColor;
}

.ep-filter-chips {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
}

.ep-chip {
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-full);
    background: var(--bg-elevated);
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    border: 1px solid transparent;
    transition: all 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-chip:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.ep-chip:active {
    transform: scale(0.96);
    transition-duration: 0.1s;
}

.ep-chip.active {
    background: var(--accent-subtle);
    color: var(--accent);
    border-color: var(--accent);
    transform: scale(1.02);
}

.ep-plans-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--space-4);
    flex: 1;
    align-content: start;
}

/* ========================================
   4. PLAN CARDS
======================================== */
.ep-plan-card {
    display: flex;
    flex-direction: column;
    padding: var(--space-5);
    background: var(--bg-elevated);
    border-radius: var(--radius-lg);
    border: 1px solid transparent;
    transition: all 0.3s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-plan-card:hover {
    transform: translateY(-4px) scale(1.01);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-subtle);
}

.ep-plan-card:active {
    transform: translateY(-1px) scale(0.99);
    transition-duration: 0.1s;
}

.ep-plan-card-header {
    display: flex;
    align-items: flex-start;
    gap: var(--space-3);
    margin-bottom: var(--space-3);
}

.ep-plan-icon {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-subtle);
    border-radius: var(--radius-md);
    flex-shrink: 0;
}

.ep-plan-icon svg {
    width: 22px;
    height: 22px;
    stroke: var(--accent);
}

.ep-plan-title {
    flex: 1;
    font-size: 15px;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
}

.ep-plan-grade {
    padding: var(--space-1) var(--space-2);
    background: var(--bg-hover);
    border-radius: var(--radius-sm);
    font-size: 11px;
    font-weight: 600;
    color: var(--text-secondary);
}

.ep-plan-date {
    font-size: 12px;
    color: var(--text-tertiary);
    margin-bottom: var(--space-3);
}

.ep-plan-mastery {
    margin-bottom: var(--space-2);
}

.ep-plan-mastery-label {
    font-size: 11px;
    color: var(--text-tertiary);
    margin-bottom: var(--space-1);
}

.ep-plan-mastery-bar {
    height: 6px;
    background: var(--bg-secondary);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.ep-plan-mastery-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--brand-primary));
    border-radius: var(--radius-full);
    transition: width 0.8s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-plan-lessons {
    font-size: 12px;
    color: var(--text-tertiary);
}

/* ========================================
   5. EMPTY STATE (.ep-empty-state)
======================================== */
.ep-empty-state {
    grid-column: 1 / -1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-12);
    text-align: center;
}

.ep-empty-icon {
    width: 64px;
    height: 64px;
    color: var(--text-tertiary);
    margin-bottom: var(--space-4);
    opacity: 0.6;
}

.ep-empty-state h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0 0 var(--space-2);
}

.ep-empty-state p {
    font-size: 14px;
    color: var(--text-secondary);
    margin: 0 0 var(--space-5);
}

/* ========================================
   6. WIZARD (.ep-wizard)
======================================== */
.ep-wizard {
    display: flex;
    flex-direction: column;
    height: 100%;
    padding: var(--space-6);
    overflow: auto;
}

.ep-wizard-step {
    max-width: 640px;
    margin: 0 auto;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: var(--space-5);
    animation: ep-wizardStep 0.4s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.ep-back-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-3);
    background: transparent;
    font-size: 13px;
    font-weight: 500;
    color: var(--text-tertiary);
    border-radius: var(--radius-md);
    border: none;
    align-self: flex-start;
    transition: var(--transition-fast);
}

.ep-back-btn:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.ep-back-btn svg {
    width: 16px;
    height: 16px;
}

.ep-wizard-step h2 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
    letter-spacing: -0.02em;
}

.ep-wizard-subtitle {
    font-size: 14px;
    color: var(--text-tertiary);
    margin: calc(-1 * var(--space-3)) 0 0;
}

.ep-subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: var(--space-3);
}

.ep-subject-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-4) var(--space-3);
    background: var(--bg-elevated);
    border-radius: var(--radius-lg);
    border: 1px solid transparent;
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    transition: all 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-subject-btn:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
    border-color: var(--accent-subtle);
    transform: translateY(-3px) scale(1.04);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.ep-subject-btn:active {
    transform: scale(0.97);
    transition-duration: 0.1s;
}

.ep-subject-btn:active,
.ep-subject-btn.selected {
    background: var(--accent-subtle);
    color: var(--accent);
}

.ep-subject-icon {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.ep-subject-icon svg {
    width: 24px;
    height: 24px;
    stroke: currentColor;
}

.ep-grade-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-2);
}

.ep-grade-btn {
    padding: var(--space-4) var(--space-3);
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 600;
    color: var(--text-secondary);
    border: 1px solid transparent;
    transition: all 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-grade-btn:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
    transform: translateY(-2px) scale(1.03);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.ep-grade-btn:active {
    transform: scale(0.97);
    transition-duration: 0.1s;
}

.ep-grade-btn.selected {
    background: var(--accent-subtle);
    color: var(--accent);
}

.ep-date-input-container {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.ep-date-input {
    padding: var(--space-3) var(--space-4);
    background: var(--bg-elevated);
    border: 1px solid var(--bg-hover);
    border-radius: var(--radius-md);
    font-size: 14px;
    color: var(--text-primary);
    max-width: 240px;
}

.ep-date-input:focus {
    outline: none;
    border-color: var(--accent);
}

.ep-days-counter {
    font-size: 13px;
    color: var(--text-tertiary);
}

.ep-next-btn {
    padding: var(--space-3) var(--space-5);
    background: var(--brand-primary);
    color: #000;
    font-size: 14px;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    transition: var(--transition-fast);
    align-self: flex-start;
}

.ep-next-btn:hover:not(:disabled) {
    background: var(--brand-primary-hover);
}

.ep-next-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.ep-topic-input-container {
    display: flex;
    gap: var(--space-3);
    flex-wrap: wrap;
}

.ep-topic-input {
    flex: 1;
    min-width: 200px;
    padding: var(--space-3) var(--space-4);
    background: var(--bg-elevated);
    border: 1px solid var(--bg-hover);
    border-radius: var(--radius-md);
    font-size: 14px;
    color: var(--text-primary);
}

.ep-topic-input:focus {
    outline: none;
    border-color: var(--accent);
}

.ep-generate-btn {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-4);
    background: var(--brand-primary);
    color: #000;
    font-size: 14px;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: none;
    transition: var(--transition-fast);
}

.ep-generate-btn:hover {
    background: var(--brand-primary-hover);
}

.ep-generate-btn svg {
    width: 18px;
    height: 18px;
}

.ep-topic-suggestions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
}

.ep-suggestion-chip {
    padding: var(--space-2) var(--space-3);
    background: var(--bg-elevated);
    border-radius: var(--radius-full);
    font-size: 12px;
    color: var(--text-secondary);
    border: none;
    transition: all 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-suggestion-chip:hover {
    background: var(--accent-subtle);
    color: var(--accent);
    transform: translateY(-1px) scale(1.04);
}

.ep-suggestion-chip:active {
    transform: scale(0.96);
    transition-duration: 0.1s;
}

.ep-loading-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-12);
    gap: var(--space-4);
    animation: ep-fadeInUp 0.5s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.ep-loading-spinner {
    width: 48px;
    height: 48px;
    border: 3px solid var(--bg-elevated);
    border-top-color: var(--brand-primary);
    border-radius: 50%;
    animation: ep-spin 0.7s cubic-bezier(0.4, 0.15, 0.6, 0.85) infinite;
}

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

.ep-loading-text {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
}

.ep-loading-subtext {
    font-size: 13px;
    color: var(--text-tertiary);
}

/* ========================================
   7. SKILL TREE (.ep-skill-tree)
======================================== */
.ep-skill-tree {
    display: flex;
    flex-direction: column;
    height: 100%;
    padding: var(--space-6);
    overflow: auto;
    animation: ep-fadeInUp 0.4s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.ep-tree-header {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    margin-bottom: var(--space-6);
}

.ep-tree-info {
    flex: 1;
}

.ep-tree-info h2 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0 0 var(--space-2);
}

.ep-tree-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
}

.ep-tree-badge {
    padding: var(--space-1) var(--space-2);
    background: var(--bg-elevated);
    border-radius: var(--radius-sm);
    font-size: 11px;
    font-weight: 600;
    color: var(--text-secondary);
}

.ep-delete-plan-btn {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: transparent;
    border-radius: var(--radius-md);
    color: var(--text-tertiary);
    transition: var(--transition-fast);
}

.ep-delete-plan-btn:hover {
    background: var(--destructive-subtle);
    color: var(--destructive);
}

.ep-delete-plan-btn svg {
    width: 18px;
    height: 18px;
}

/* Mastery Ring */
.ep-mastery-ring {
    position: relative;
    width: 120px;
    height: 120px;
    margin: 0 auto var(--space-4);
}

.ep-ring-svg {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

.ep-ring-bg {
    fill: none;
    stroke: var(--bg-elevated);
    stroke-width: 8;
}

.ep-ring-fill {
    fill: none;
    stroke: var(--brand-primary);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 326.73;
    stroke-dashoffset: 326.73;
    transition: stroke-dashoffset 1.2s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-ring-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
}

.ep-tree-topic-name {
    font-size: 16px;
    font-weight: 600;
    color: var(--text-primary);
    text-align: center;
    margin-bottom: var(--space-1);
}

.ep-tree-level {
    font-size: 12px;
    color: var(--text-tertiary);
    text-align: center;
    margin-bottom: var(--space-6);
}

/* Path Container - S-curve winding layout (nodes as direct children) */
.ep-path-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-4) var(--space-6);
    max-width: 320px;
    margin: 0 auto;
}

.ep-path-node {
    position: relative;
    width: 64px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-md);
    background: var(--bg-elevated);
    flex-shrink: 0;
    transition: all 0.3s cubic-bezier(0.22, 1, 0.36, 1);
    cursor: pointer;
}

.ep-path-node:hover {
    transform: scale(1.1);
}

.ep-path-node:active {
    transform: scale(0.95);
    transition-duration: 0.1s;
}

/* S-curve: alternate left, center, right, center via align-self */
.ep-path-node:nth-child(4n+1) { align-self: flex-start; }
.ep-path-node:nth-child(4n+2) { align-self: center; }
.ep-path-node:nth-child(4n+3) { align-self: flex-end; }
.ep-path-node:nth-child(4n)   { align-self: center; }

/* Connector line above each node */
.ep-path-node::before {
    content: '';
    position: absolute;
    top: -22px;
    left: 50%;
    transform: translateX(-50%);
    width: 2px;
    height: 22px;
    background: var(--bg-hover);
}

.ep-path-node:first-child::before {
    display: none;
}

.ep-path-node svg {
    width: 24px;
    height: 24px;
}

/* Node states */
.ep-node-available {
    background: var(--accent-subtle);
    border: 2px solid var(--accent);
    animation: ep-nodeGlow 2.5s ease-in-out infinite;
}

.ep-node-available svg {
    stroke: var(--accent);
}

.ep-node-completed {
    background: var(--success-subtle);
    border: 2px solid var(--success);
}

.ep-node-completed svg {
    stroke: var(--success);
}

.ep-node-locked {
    background: var(--bg-secondary);
    border: 2px solid var(--bg-hover);
    opacity: 0.7;
}

.ep-node-locked svg {
    stroke: var(--text-tertiary);
}

/* ========================================
   8. LESSON VIEW (.ep-lesson)
======================================== */
.ep-lesson {
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow: hidden;
}

.ep-lesson-header {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4) var(--space-6);
    flex-shrink: 0;
    border-bottom: 1px solid var(--bg-hover);
}

.ep-lesson-badge {
    padding: var(--space-1) var(--space-3);
    background: var(--accent-subtle);
    color: var(--accent);
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.5px;
    border-radius: var(--radius-sm);
}

.ep-lesson-messages {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-5);
    display: flex;
    flex-direction: column;
    gap: var(--space-4);
}

.ep-lesson-msg {
    max-width: 85%;
    padding: var(--space-4);
    border-radius: var(--radius-lg);
    font-size: 14px;
    line-height: 1.6;
    animation: ep-msgSlideIn 0.35s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.ep-lesson-msg.ai {
    align-self: flex-start;
    background: var(--bg-elevated);
    color: var(--text-primary);
    display: flex;
    align-items: flex-start;
    gap: var(--space-3);
}

.ep-msg-avatar {
    flex-shrink: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-subtle);
    border-radius: var(--radius-md);
    color: var(--accent);
}

.ep-msg-content {
    flex: 1;
    min-width: 0;
}

.ep-msg-actions {
    flex-shrink: 0;
    display: flex;
    gap: var(--space-1);
}

.ep-msg-thumb {
    padding: var(--space-1);
    background: transparent;
    border: none;
    cursor: pointer;
    font-size: 14px;
    opacity: 0.6;
    transition: var(--transition-fast);
}

.ep-msg-thumb:hover {
    opacity: 1;
}

.ep-lesson-msg.student {
    align-self: flex-end;
    background: var(--accent-subtle);
    color: var(--text-primary);
}

[data-theme="dark"] .ep-lesson-msg.student {
    background: var(--accent-subtle);
}

.ep-lesson-suggestions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
    padding: 0 var(--space-5) var(--space-3);
}

.ep-lesson-suggestion-chip {
    padding: var(--space-2) var(--space-4);
    background: var(--bg-elevated);
    border-radius: var(--radius-full);
    font-size: 13px;
    color: var(--text-secondary);
    border: 1px solid transparent;
    transition: all 0.25s cubic-bezier(0.22, 1, 0.36, 1);
}

.ep-lesson-suggestion-chip:hover {
    background: var(--accent-subtle);
    color: var(--accent);
    transform: translateY(-1px) scale(1.03);
}

.ep-lesson-suggestion-chip:active {
    transform: scale(0.96);
    transition-duration: 0.1s;
}

.ep-lesson-bottom {
    padding: var(--space-4) var(--space-6);
    flex-shrink: 0;
    border-top: 1px solid var(--bg-hover);
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
}

.ep-lesson-actions {
    display: flex;
    gap: var(--space-2);
}

.ep-lesson-more-btn,
.ep-lesson-finish-btn {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    font-size: 13px;
    font-weight: 500;
    color: var(--text-secondary);
    border: none;
    transition: var(--transition-fast);
}

.ep-lesson-more-btn:hover,
.ep-lesson-finish-btn:hover {
    background: var(--bg-hover);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.ep-lesson-more-btn:active,
.ep-lesson-finish-btn:active {
    transform: scale(0.96);
    transition-duration: 0.1s;
}

.ep-lesson-finish-btn {
    background: var(--success-subtle);
    color: var(--success);
}

.ep-lesson-finish-btn:hover {
    background: var(--success);
    color: #fff;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(34, 197, 94, 0.2);
}

.ep-lesson-input-bar {
    display: flex;
    gap: var(--space-2);
    align-items: center;
}

.ep-lesson-input-bar input {
    flex: 1;
    padding: var(--space-3) var(--space-4);
    background: var(--bg-elevated);
    border: 1px solid var(--bg-hover);
    border-radius: var(--radius-md);
    font-size: 14px;
    color: var(--text-primary);
}

.ep-lesson-input-bar input:focus {
    outline: none;
    border-color: var(--accent);
}

.ep-lesson-send-btn {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--brand-primary);
    color: #000;
    border-radius: var(--radius-md);
    border: none;
    transition: var(--transition-fast);
}

.ep-lesson-send-btn:hover {
    background: var(--brand-primary-hover);
}

.ep-lesson-send-btn svg {
    width: 18px;
    height: 18px;
}

/* Loading dots for AI typing */
.ep-loading-dots {
    display: flex;
    gap: var(--space-1);
    padding: var(--space-4);
}

.ep-loading-dots span {
    width: 8px;
    height: 8px;
    background: var(--text-tertiary);
    border-radius: 50%;
    animation: ep-bounce 1.4s ease-in-out infinite both;
}

.ep-loading-dots span:nth-child(1) { animation-delay: -0.32s; }
.ep-loading-dots span:nth-child(2) { animation-delay: -0.16s; }

@keyframes ep-fadeIn {
    from { opacity: 0; transform: translateX(-50%) translateY(8px); }
    to { opacity: 1; transform: translateX(-50%) translateY(0); }
}

@keyframes ep-bounce {
    0%, 80%, 100% { transform: scale(0.6); opacity: 0.5; }
    40% { transform: scale(1); opacity: 1; }
}

/* ========================================
   9. EXAM PREP SECTION
======================================== */
.exam-prep-section {
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow: hidden;
}

.exam-prep-section.hidden {
    display: none;
}

/* ========================================
   RESPONSIVE - Mobile (max-width 768px)
======================================== */
@media (max-width: 768px) {
    .app-sidebar {
        width: 76px;
        padding: var(--space-2);
    }

    .sidebar-brand {
        padding: var(--space-2);
        font-size: 9px;
        text-align: center;
        line-height: 1.1;
    }

    .sidebar-item span,
    .sidebar-bottom .sidebar-item span {
        display: none;
    }

    .sidebar-item {
        justify-content: center;
        padding: var(--space-3);
    }

    .sidebar-nav,
    .sidebar-bottom {
        padding: var(--space-2);
    }

    .sidebar-upgrade {
        padding: var(--space-2);
    }

    .sidebar-upgrade-btn {
        justify-content: center;
        padding: var(--space-3);
    }

    .sidebar-upgrade-text {
        display: none;
    }

    .ep-dashboard {
        padding: var(--space-4);
    }

    .ep-dashboard-header {
        flex-direction: column;
        align-items: stretch;
    }

    .ep-search-bar {
        min-width: 0;
    }

    .ep-plans-grid {
        grid-template-columns: 1fr;
    }

    .ep-wizard {
        padding: var(--space-4);
    }

    .ep-subject-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .ep-grade-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .ep-skill-tree {
        padding: var(--space-4);
    }

    .ep-path-node:nth-child(4n+1),
    .ep-path-node:nth-child(4n+2),
    .ep-path-node:nth-child(4n+3),
    .ep-path-node:nth-child(4n) {
        align-self: center; /* Stack centered on mobile */
    }

    .ep-lesson-header,
    .ep-lesson-bottom {
        padding: var(--space-3) var(--space-4);
    }

    .ep-lesson-messages {
        padding: var(--space-4);
    }
}

/* Alternative: Bottom tab bar on very small screens */
@media (max-width: 480px) {
    .app-container {
        flex-direction: column;
    }

    .app-sidebar {
        width: 100%;
        height: 60px;
        flex-direction: row;
        justify-content: space-around;
        align-items: center;
        padding: 0 var(--space-2);
        padding-bottom: env(safe-area-inset-bottom, 0);
        border-right: none;
        border-top: 1px solid var(--border-default);
        order: 2;
        position: fixed;
        bottom: 0;
        left: 0;
        right: 0;
        z-index: 200;
        background: var(--bg-glass);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
    }

    .app-main {
        padding-bottom: calc(60px + env(safe-area-inset-bottom, 0));
    }

    .sidebar-brand {
        display: none;
    }

    .sidebar-nav {
        flex-direction: row;
        flex: 1;
        justify-content: center;
        padding: 0;
        gap: var(--space-1);
    }

    .sidebar-bottom {
        border-top: none;
        padding: 0;
        flex-direction: row;
        margin-top: 0;
    }

    .sidebar-item {
        flex-direction: column;
        padding: var(--space-2);
        border-radius: var(--radius-md);
        min-width: 48px;
        min-height: 48px;
        justify-content: center;
        align-items: center;
    }

    .sidebar-item svg {
        width: 22px;
        height: 22px;
    }

    .sidebar-item span {
        display: none;
    }

    .sidebar-item.active {
        box-shadow: none;
    }

    .sidebar-upgrade {
        display: none !important;
    }

    .exam-prep-section {
        padding-bottom: calc(60px + env(safe-area-inset-bottom, 0));
    }

    .ep-lesson-msg {
        max-width: 95%;
        padding: var(--space-3);
        font-size: 13px;
    }

    .ep-wizard-step h2 {
        font-size: 1.25rem;
    }

    .ep-topic-input-container {
        flex-direction: column;
    }

    .ep-topic-input {
        min-width: auto;
        font-size: 16px;
    }

    .ep-date-input {
        font-size: 16px;
        max-width: none;
        width: 100%;
    }

    .ep-next-btn {
        width: 100%;
        min-height: 48px;
        justify-content: center;
        display: flex;
        align-items: center;
    }

    .ep-generate-btn {
        width: 100%;
        min-height: 48px;
        justify-content: center;
    }

    .ep-new-exam-btn {
        min-height: 44px;
    }

    .ep-search-bar {
        min-height: 44px;
    }

    .ep-search-bar input {
        font-size: 16px;
    }
}