:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #dbeafe;
    --success: #059669;
    --success-light: #ecfdf5;
    --warning: #d97706;
    --warning-light: #fef3c7;
    --danger: #dc2626;
    --gray-50: #f8fafc;
    --gray-100: #f1f5f9;
    --gray-200: #e2e8f0;
    --gray-300: #cbd5e1;
    --gray-600: #475569;
    --gray-700: #334155;
    --gray-800: #1e293b;
    --gray-900: #0f172a;
    --blue-50: #eff6ff;
    --blue-100: #dbeafe;
    --blue-200: #bfdbfe;
    --blue-600: #2563eb;
    --blue-700: #1d4ed8;
    --vh: 1vh;
}

* {
    user-select: none;
    -webkit-user-select: none;
    -ms-user-select: none;
}

body {
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    overflow: hidden;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

.app-container {
    display: grid;
    grid-template-rows: auto 1fr auto;
    height: 100vh;
    overflow: hidden;
    margin-left: 20px;
    margin-right: 20px;

}

/* Compact Professional Header */
.header {
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    padding: 0.75rem 1rem;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.1);
    z-index: 20;
    text-align: center;
    position: relative;
    border-bottom: 1px solid var(--blue-200);
    margin-left: 20px;
    margin-right: 20px;
}

.header-content {
    margin: 10 auto;
    border-radius: 0.75rem;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    padding: 1rem;
    border: 1px solid var(--blue-200);
    box-shadow: 0 4px 16px rgba(37, 99, 235, 0.08);
    position: relative;
}

.header-content h1 {
    background: linear-gradient(135deg, var(--primary), var(--blue-700));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-size: 1.5rem;
    font-weight: 700;
    margin: 0;
    letter-spacing: -0.025em;
}

.header-content .h-px {
    height: 1px;
    background: var(--blue-200);
    margin: 0.5rem 0;
    border-radius: 1px;
}

.header-content p {
    color: var(--gray-600);
    font-size: 0.875rem;
    font-weight: 600;
    margin: 0;
}

.progress-bar {
    height: 0.5rem;
    background: var(--blue-100);
    border-radius: 0.5rem;
    overflow: hidden;
    margin-top: 0.75rem;
    position: relative;
    border: 1px solid var(--blue-200);
}

.progress {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--blue-700));
    transition: width 0.3s ease;
    border-radius: 0.5rem;
}

/* Compact main content */
.main-content {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
    overflow: hidden;
    padding: 1rem;
    height: 100%;
    transition: grid-template-columns 0.3s ease;
}

@media (min-width: 1025px) {
    .main-content.panel-visible {
        grid-template-columns: 1fr 280px;
    }
}

.question-section {
    overflow-y: auto;
    padding-right: 0.5rem;
    -ms-overflow-style: none;
    scrollbar-width: thin;
    scrollbar-color: var(--primary) var(--blue-100);
}

.question-section::-webkit-scrollbar {
    width: 6px;
}

.question-section::-webkit-scrollbar-track {
    background: var(--blue-100);
    border-radius: 3px;
}

.question-section::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: 3px;
}

.question-card {
    background: white;
    border-radius: 0.75rem;
    padding: 0.5rem;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.1);
    margin-bottom: 1rem;
    border: 1px solid var(--blue-100);
    margin-left: 10px;
    margin-right: 10px;
}

/* Compact question panel */
.question-panel {
    background: white;
    border-radius: 0.75rem;
    padding: 0.5rem;
    box-shadow: -2px 0 8px rgba(37, 99, 235, 0.1);
    overflow-y: auto;
    max-height: calc(100vh - 180px);
    scrollbar-width: thin;
    scrollbar-color: var(--primary) var(--blue-100);
    transition: all 0.3s ease;
    border: 1px solid var(--blue-200);
    position: fixed;
    top: 20%;
    right: -350px;
    width: 280px;
    height: auto;
    max-height: 60vh;
    z-index: 35;
    opacity: 0;
    visibility: hidden;
      margin-left: 10px;
    margin-right: 10px;
}

.question-panel.hidden {
    opacity: 0;
    visibility: hidden;
    transform: translateX(100%);
}

.panel-close-btn {
    background: none;
    border: none;
    font-size: 1.1rem;
    color: var(--gray-600);
    cursor: pointer;
    padding: 0.25rem;
    border-radius: 0.25rem;
    transition: all 0.2s ease;
}

.panel-close-btn:hover {
    background: var(--blue-50);
    color: var(--gray-800);
}

.question-panel::-webkit-scrollbar {
    width: 6px;
}

.question-panel::-webkit-scrollbar-track {
    background: var(--blue-100);
    border-radius: 3px;
}

.question-panel::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: 3px;
}

.option {
    padding: 0.75rem 1rem;
    border: 2px solid var(--blue-200);
    border-radius: 0.5rem;
    margin: 0.5rem 0;
    cursor: pointer;
    transition: all 0.2s ease;
    background: white;
    font-size: 0.9rem;
}

.option:hover {
    border-color: var(--primary);
    background: var(--blue-50);
    transform: translateY(-1px);
}

.option.selected {
    border-color: var(--success);
    background: var(--success-light);
}

.option.correct {
    background-color: var(--success);
    color: white;
    border-color: var(--success);
}

.option.incorrect {
    background-color: var(--danger);
    color: white;
    border-color: var(--danger);
}

/* Compact question grid */
.question-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
    gap: 0.5rem;
    padding: 0.75rem 0;
}

.question-number {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 0.375rem;
    font-weight: 600;
    font-size: 0.85rem;
    transition: all 0.2s ease;
    border: 2px solid var(--blue-200);
    background: white;
    cursor: pointer;
}

.question-number:hover {
    transform: scale(1.05);
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.15);
}

.question-number.current {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.question-number.attempted {
    background: var(--success);
    color: white;
    border-color: var(--success);
}

.question-number.marked {
    background: var(--warning);
    color: white;
    border-color: var(--warning);
}

/* Compact footer */
.footer {
    background: white;
    padding: 0.5rem;
    box-shadow: 0 -2px 8px rgba(37, 99, 235, 0.1);
    position: sticky;
    bottom: 0;
    z-index: 20;
    border-top: 1px solid var(--blue-200);
}

.footer-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.5rem;
    margin-bottom: 0.75rem;
}

.footer-actions {
    display: grid;
    grid-template-columns: auto 1fr auto;
    gap: 0.5rem;
    align-items: center;
}

/* Compact button styling */
.button {
    padding: 0.4rem 0.5rem;
    border-radius: 0.5rem;
    font-weight: 400;
    font-size: 0.575rem;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.375rem;
    border: 1px solid var(--blue-200);
    box-shadow: 0 1px 3px rgba(37, 99, 235, 0.1);
    cursor: pointer;
    background: white;
    color: var(--gray-700);
}

.button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.button-primary {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.button-primary:hover:not(:disabled) {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

.button-success {
    background: var(--success);
    color: white;
    border-color: var(--success);
}

.button-success:hover:not(:disabled) {
    background: #047857;
    transform: translateY(-1px);
}

.button-warning {
    background: var(--warning);
    color: white;
    border-color: var(--warning);
}

.button-warning:hover:not(:disabled) {
    background: #b45309;
    transform: translateY(-1px);
}

.button:hover:not(:disabled) {
    background: var(--blue-50);
    border-color: var(--primary);
    transform: translateY(-1px);
}

.button i {
    font-size: 1rem;
}

.button:has(> i:only-child) {
    padding: 0.5rem;
    width: 2rem;
    height: 2rem;
}

.explanation {
    background: var(--blue-50);
    border-radius: 0.5rem;
    padding: 1rem;
    margin-top: 1rem;
    transition: all 0.3s ease;
    border: 1px solid var(--blue-200);
    font-size: 0.9rem;
}

.explanation-container {
    margin-top: 1rem;
    padding: 1rem;
    border-radius: 0.5rem;
    background-color: var(--blue-50);
    border: 1px solid var(--blue-200);
}

.explanation-container.hidden {
    display: none;
}

.backdrop {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(15, 23, 42, 0.4);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 25;
}

.backdrop.show {
    opacity: 1;
    visibility: visible;
}

/* Compact View Mode Selector */
.view-mode-selector {
    display: flex;
    gap: 0.375rem;
    margin-top: 0.75rem;
    justify-content: center;
    flex-wrap: wrap;
}

.mode-btn {
    padding: 0.5rem 0.875rem;
    border-radius: 0.5rem;
    font-weight: 600;
    font-size: 0.8rem;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 0.25rem;
    border: 2px solid var(--blue-200);
    background: white;
    color: var(--gray-600);
    cursor: pointer;
}

.mode-btn:hover {
    background: var(--blue-50);
    transform: translateY(-1px);
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.15);
}

.mode-btn.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.3);
}

.mode-btn i {
    font-size: 0.9rem;
}

/* Compact Review Mode */
.option-review {
    padding: 0.6rem 0.875rem;
    border: 2px solid var(--blue-200);
    border-radius: 0.5rem;
    margin: 0.375rem 0;
    background: white;
    transition: all 0.2s ease;
    font-size: 0.9rem;
}

.option-review.correct-option {
    border-color: var(--success);
    background: var(--success-light);
    font-weight: 600;
}

.answer-section {
    animation: slideDown 0.3s ease;
}

.explanation-section {
    animation: slideDown 0.3s ease;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Compact Study Mode */
.study-navigation {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem;
    background: white;
    border-radius: 0.5rem;
    margin-top: 1rem;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.1);
    border: 1px solid var(--blue-200);
}

/* Desktop panel visibility */
@media (min-width: 1025px) {
    .question-panel {
        position: static;
        transform: none;
        right: auto;
        top: auto;
        width: auto;
        max-height: calc(100vh - 180px);
        opacity: 1;
        visibility: visible;
        display: none;
          margin-left: 10px;
    margin-right: 10px;
    }

    .question-panel.show {
        display: block;
    }

    .question-panel.hidden {
        display: none;
        transform: none;
    }
}

/* Enhanced Mobile Responsiveness */
@media (max-width: 1024px) {
    .main-content {
        grid-template-columns: 1fr !important;
        padding: 0.75rem;
          margin-left: 10px;
    margin-right: 10px;
    }

    .question-panel {
        position: fixed;
        bottom: 0;
        left: 0;
        right: 0;
        top: auto;
        width: 100%;
        max-height: 45vh;
        max-height: calc(var(--vh, 1vh) * 45);
        border-radius: 0.75rem 0.75rem 0 0;
        transform: translateY(100%);
        transition: transform 0.3s ease, opacity 0.3s ease, visibility 0.3s ease;
        z-index: 30;
        height: auto;
        overflow-y: auto;
        -webkit-overflow-scrolling: touch;
        opacity: 0;
        visibility: hidden;
        padding: 1rem;
          margin-left: 10px;
    margin-right: 10px;
    }

    .question-panel.show {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }

    .question-panel.hidden {
        transform: translateY(100%);
        opacity: 0;
        visibility: hidden;
    }
    
    .question-panel .question-grid {
        display: grid !important;
        grid-template-columns: repeat(6, 1fr) !important;
        gap: 0.375rem !important;
        padding: 0.75rem 0 !important;
        width: 100% !important;
        box-sizing: border-box !important;
    }

    .header {
        padding: env(safe-area-inset-top, 0.75rem) 0.75rem 0.75rem;
    }

    .header-content {
        padding: 0.75rem;
        margin: 0 0.25rem;
    }

    .header-content h1 {
        font-size: 1.25rem;
    }

    .header-content p {
        font-size: 0.8rem;
    }

    .progress-bar {
        margin-top: 0.5rem;
        height: 0.375rem;
    }

    .view-mode-selector {
        gap: 0.25rem;
        margin-top: 0.5rem;
    }
    
    .mode-btn {
        padding: 0.375rem 0.625rem;
        font-size: 0.75rem;
        flex: 1;
        justify-content: center;
        min-width: 0;
    }
    
    .mode-btn span {
        display: none;
    }
    
    .mode-btn i {
        font-size: 0.8rem;
    }

    .question-card {
        padding: 1rem;
    }

    .footer {
        padding: 0.75rem;
        padding-bottom: env(safe-area-inset-bottom, 0.75rem);
    }
}

@media (max-width: 640px) {
    .question-grid {
        grid-template-columns: repeat(6, 1fr) !important;
        gap: 0.3rem !important;
        padding: 0.5rem 0 !important;
    }
    
    .question-number {
        font-size: 0.75rem !important;
        min-width: 26px !important;
        min-height: 26px !important;
        border-radius: 0.25rem !important;
    }
    
    .question-panel {
        padding: 0.75rem !important;
        max-height: 40vh !important;
        max-height: calc(var(--vh, 1vh) * 40) !important;
          margin-left: 10px;
    margin-right: 10px;
    }

    .header-content {
        padding: 0.5rem;
    }

    .header-content h1 {
        font-size: 1.1rem;
    }

    .main-content {
        padding: 0.5rem;
    }
}

@media (max-width: 480px) {
    .question-grid {
        grid-template-columns: repeat(5, 1fr) !important;
        gap: 0.25rem !important;
    }
    
    .question-number {
        font-size: 0.7rem !important;
        min-width: 24px !important;
        min-height: 24px !important;
    }
    
    .question-panel {
        max-height: 35vh !important;
        max-height: calc(var(--vh, 1vh) * 35) !important;
        padding: 0.5rem !important;
          margin-left: 10px;
    margin-right: 10px;
    }

    .mode-btn {
        padding: 0.25rem 0.5rem;
        border-radius: 0.375rem;
    }
}

@media (max-width: 360px) {
    .question-grid {
        grid-template-columns: repeat(5, 1fr) !important;
        gap: 0.2rem !important;
    }
    
    .question-number {
        font-size: 0.65rem !important;
        min-width: 22px !important;
        min-height: 22px !important;
    }

    .header-content {
        padding: 0.375rem;
        margin: 0;
        border-radius: 0.5rem;
    }
}

/* iOS specific fixes */
@supports (-webkit-touch-callout: none) {
    .question-panel.show {
        -webkit-transform: translateY(0) translateZ(0);
        transform: translateY(0) translateZ(0);
    }
    
    .question-grid {
        -webkit-transform: translateZ(0);
        transform: translateZ(0);
    }

    .header {
        padding-top: max(env(safe-area-inset-top), 0.75rem);
    }
    
    .footer {
        padding-bottom: max(env(safe-area-inset-bottom), 0.75rem);
    }
}

/* Landscape mode adjustments */
@media screen and (max-width: 900px) and (orientation: landscape) {
    .question-grid {
        grid-template-columns: repeat(8, 1fr) !important;
        gap: 0.25rem !important;
        padding: 0.375rem 0 !important;
    }
    
    .question-number {
        font-size: 0.65rem !important;
        min-width: 20px !important;
        min-height: 20px !important;
    }
    
    .question-panel {
        max-height: 55vh !important;
        max-height: calc(var(--vh, 1vh) * 55) !important;
    }

    .header {
        padding: 0.5rem 0.75rem;
    }
    
    .header-content {
        padding: 0.5rem 0.75rem;
    }
    
    .progress-bar {
        height: 0.25rem;
        margin-top: 0.375rem;
    }
}

/* Enhanced scrolling */
#review-view {
    max-height: calc(100vh - 250px);
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: var(--primary) var(--blue-100);
}

#review-view::-webkit-scrollbar {
    width: 6px;
}

#review-view::-webkit-scrollbar-track {
    background: var(--blue-100);
    border-radius: 3px;
}

#review-view::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: 3px;
}

/* Loading states */
.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 150px;
    font-size: 1rem;
    color: var(--gray-600);
}

.loading::after {
    content: '';
    width: 18px;
    height: 18px;
    border: 2px solid var(--blue-200);
    border-top: 2px solid var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-left: 0.5rem;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Enhanced accessibility */
.mode-btn:focus,
.button:focus,
.option:focus,
.option-review:focus,
.question-number:focus {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
}

.question-number:focus-visible,
.option:focus-visible,
.button:focus-visible,
.mode-btn:focus-visible {
    outline: 2px solid var(--primary);
    outline-offset: 2px;
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
}

/* Print styles */
@media print {
    .header,
    .footer,
    .question-panel,
    .view-mode-selector {
        display: none !important;
    }
    
    .main-content {
        grid-template-columns: 1fr !important;
        padding: 0 !important;
    }
    
    .question-card {
        box-shadow: none !important;
        border: 1px solid var(--gray-300) !important;
        break-inside: avoid;
        margin-bottom: 1rem !important;
    }
}

/* Smooth transitions */
.question-section {
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.question-section.hidden {
    opacity: 0;
    transform: translateY(10px);
    pointer-events: none;
}

.button:active {
    transform: translateY(1px) !important;
}

.mode-btn:active {
    transform: translateY(1px) scale(0.98) !important;
}

html {
    scroll-behavior: smooth;
}

body:not(.loaded) .app-container {
    opacity: 0;
    transform: translateY(10px);
}

body.loaded .app-container {
    opacity: 1;
    transform: translateY(0);
    transition: opacity 0.4s ease, transform 0.4s ease;
}

/* Error states */
.error-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 200px;
    text-align: center;
    color: var(--danger);
}

.error-state i {
    font-size: 2.5rem;
    margin-bottom: 0.75rem;
    opacity: 0.7;
}

.error-state h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.error-state p {
    color: var(--gray-600);
    margin-bottom: 0.75rem;
    font-size: 0.9rem;
}

.retry-button {
    background: var(--primary);
    color: white;
    padding: 0.6rem 1.25rem;
    border-radius: 0.5rem;
    border: none;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.875rem;
    transition: all 0.2s ease;
}

.retry-button:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}