:root {
    --bg-color: #0f172a;
    --panel-bg: rgba(30, 41, 59, 0.7);
    --panel-border: rgba(255, 255, 255, 0.1);
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --accent: #ec4899;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --success: #10b981;
    --danger: #ef4444;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Outfit', sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow: hidden;
}

/* Dynamic mesh background */
.background-mesh {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    background: 
        radial-gradient(circle at 15% 50%, rgba(99, 102, 241, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 85% 30%, rgba(236, 72, 153, 0.15) 0%, transparent 50%);
    filter: blur(60px);
    animation: pulse 10s infinite alternate;
}

@keyframes pulse {
    0% { transform: scale(1); opacity: 0.8; }
    100% { transform: scale(1.1); opacity: 1; }
}

.app-container {
    width: 100%;
    max-width: 800px;
    padding: 20px;
    position: relative;
    z-index: 1;
}

.glass-panel {
    background: var(--panel-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--panel-border);
    border-radius: 24px;
    padding: 40px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    transition: opacity 0.4s ease, transform 0.4s ease, filter 0.4s ease;
    max-height: 90vh;
    overflow-y: auto;
}

/* Custom Scrollbar for sleek aesthetic */
.glass-panel::-webkit-scrollbar {
    width: 6px;
}
.glass-panel::-webkit-scrollbar-track {
    background: transparent;
    margin: 10px;
}
.glass-panel::-webkit-scrollbar-thumb {
    background: rgba(99, 102, 241, 0.5);
    border-radius: 10px;
}
.glass-panel::-webkit-scrollbar-thumb:hover {
    background: rgba(99, 102, 241, 0.8);
}

.glass-panel.hidden {
    opacity: 0;
    pointer-events: none;
    transform: translateY(20px);
    position: absolute;
    top: -9999px; /* Hack to remove from flow but keep transitions */
    left: 0; 
    right: 0; 
}

.hidden {
    display: none !important;
}
section:not(.active) {
    display: none;
}
section.active {
    display: block;
    animation: slideUp 0.5s ease forwards;
}

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

.app-header {
    text-align: center;
    margin-bottom: 30px;
}

.logo {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 12px;
    margin-bottom: 10px;
}

.logo h1 {
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(to right, #a5b4fc, #fbcfe8);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.icon-accent {
    font-size: 2.5rem;
    color: var(--primary);
}

.app-header p {
    color: var(--text-muted);
}

.api-key-container {
    margin-bottom: 20px;
}

.api-key-container input {
    width: 100%;
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--panel-border);
    border-radius: 12px;
    padding: 15px 20px;
    color: var(--text-main);
    font-size: 1rem;
    outline: none;
    transition: border-color 0.3s;
}

.api-key-container input:focus {
    border-color: var(--primary);
}

.input-tabs {
    display: flex;
    background: rgba(15, 23, 42, 0.6);
    border-radius: 12px;
    padding: 5px;
    margin-bottom: 20px;
}

.tab-btn {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-muted);
    padding: 12px;
    font-size: 1rem;
    font-weight: 500;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.tab-btn.active {
    background: var(--primary);
    color: white;
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.tab-content {
    display: none;
}
.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.drop-zone {
    border: 2px dashed rgba(99, 102, 241, 0.5);
    border-radius: 16px;
    padding: 40px 20px;
    text-align: center;
    background: rgba(15, 23, 42, 0.3);
    transition: all 0.3s ease;
    cursor: pointer;
}

.drop-zone:hover, .drop-zone.dragover {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.1);
}

.upload-icon {
    font-size: 3rem;
    color: var(--primary);
    margin-bottom: 10px;
}

.drop-zone p {
    color: var(--text-muted);
    margin-bottom: 15px;
}

.divider {
    display: block;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 15px;
}

.browse-btn {
    display: inline-block;
    background: rgba(255, 255, 255, 0.1);
    color: white;
    padding: 8px 24px;
    border-radius: 20px;
    font-size: 0.9rem;
    cursor: pointer;
    transition: background 0.2s;
}

.browse-btn:hover {
    background: rgba(255, 255, 255, 0.2);
}

.file-name {
    margin-top: 15px;
    color: #a5b4fc !important;
    font-size: 0.9rem;
    word-break: break-all;
}

.text-input-container textarea {
    width: 100%;
    height: 220px;
    background: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--panel-border);
    border-radius: 12px;
    padding: 20px;
    color: var(--text-main);
    font-size: 1rem;
    resize: none;
    outline: none;
    transition: border-color 0.3s;
}

.text-input-container textarea:focus {
    border-color: var(--primary);
}

.primary-btn {
    width: 100%;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    color: white;
    border: none;
    padding: 16px;
    font-size: 1.1rem;
    font-weight: 600;
    border-radius: 12px;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    margin-top: 25px;
    transition: transform 0.2s, box-shadow 0.2s;
    box-shadow: 0 10px 20px -5px rgba(99, 102, 241, 0.4);
}

.primary-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 25px -5px rgba(236, 72, 153, 0.4);
}

.primary-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    background: #475569;
    box-shadow: none;
}

.secondary-btn {
    background: rgba(255, 255, 255, 0.1);
    color: white;
    border: none;
    padding: 16px 24px;
    font-size: 1rem;
    font-weight: 500;
    border-radius: 12px;
    cursor: pointer;
    transition: background 0.2s;
}
.secondary-btn:hover {
    background: rgba(255, 255, 255, 0.2);
}
.secondary-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Spinner */
.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid rgba(255, 255, 255, 0.1);
    border-top: 4px solid var(--accent);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 20px auto;
}

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

/* Quiz Section specific */
.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 1px solid var(--panel-border);
}
.quiz-progress {
    flex: 1;
    margin-right: 20px;
}
#question-counter {
    display: block;
    font-size: 0.9rem;
    color: var(--text-muted);
    margin-bottom: 8px;
}
.progress-bar-container {
    height: 6px;
    background: rgba(15, 23, 42, 0.6);
    border-radius: 3px;
    overflow: hidden;
}
.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--accent));
    border-radius: 3px;
    transition: width 0.4s ease;
}
.icon-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    transition: color 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}
.icon-btn:hover {
    color: white;
}

.question-container h2 {
    font-size: 1.5rem;
    line-height: 1.4;
    margin-bottom: 25px;
    color: white;
}

.options-container {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.option-card {
    background: rgba(15, 23, 42, 0.4);
    border: 1px solid var(--panel-border);
    padding: 16px 20px;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 15px;
}

.option-card:hover {
    background: rgba(99, 102, 241, 0.1);
    border-color: rgba(99, 102, 241, 0.4);
    transform: translateX(5px);
}

.option-card.selected {
    background: rgba(99, 102, 241, 0.2);
    border-color: var(--primary);
}

.option-card.correct {
    background: rgba(16, 185, 129, 0.2);
    border-color: var(--success);
}
.option-card.wrong {
    background: rgba(239, 68, 68, 0.2);
    border-color: var(--danger);
}


.option-indicator {
    width: 24px;
    height: 24px;
    border: 2px solid var(--text-muted);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.option-card.selected .option-indicator {
    border-color: var(--primary);
    background: var(--primary);
    box-shadow: inset 0 0 0 4px rgba(15, 23, 42, 0.8);
}

.quiz-footer {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}
.quiz-footer .primary-btn {
    margin-top: 0;
    flex: 2;
}
.quiz-footer .secondary-btn {
    flex: 1;
}

.results-content {
    text-align: center;
    padding: 20px 0;
}
.success-icon {
    font-size: 5rem;
    color: #eab308;
    margin-bottom: 20px;
    animation: bounce 2s infinite;
}
.results-content h2 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    background: linear-gradient(to right, #fbbf24, #f59e0b);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}
.results-content p {
    font-size: 1.2rem;
    color: var(--text-muted);
    margin-bottom: 30px;
}
#score-display {
    color: white;
    font-weight: 700;
    font-size: 1.5rem;
}

/* Quiz Settings */
.quiz-settings {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 20px;
    background: rgba(15, 23, 42, 0.4);
    padding: 20px;
    border-radius: 12px;
    border: 1px solid var(--panel-border);
}

.setting-group {
    flex: 1;
    min-width: 120px;
}

.setting-group.topic-group {
    flex: 100%;
}

.setting-group label {
    display: block;
    margin-bottom: 8px;
    font-size: 0.9rem;
    color: var(--text-muted);
}

.setting-group select,
.setting-group input {
    width: 100%;
    background: rgba(15, 23, 42, 0.8);
    border: 1px solid var(--panel-border);
    border-radius: 8px;
    padding: 12px 15px;
    color: white;
    font-size: 1rem;
    outline: none;
    transition: border-color 0.3s;
}

.setting-group select:focus,
.setting-group input:focus {
    border-color: var(--primary);
}

/* Learning Report */
#learning-report-container {
    margin: 30px 0;
    padding: 20px;
    background: rgba(30, 41, 59, 0.6);
    border-radius: 16px;
    border: 1px solid var(--panel-border);
    text-align: left;
}

#learning-report-container h3 {
    display: flex;
    align-items: center;
    gap: 10px;
    color: #a5b4fc;
    margin-bottom: 20px;
    font-size: 1.3rem;
    border-bottom: 1px solid var(--panel-border);
    padding-bottom: 15px;
}

.tutor-card {
    background: rgba(15, 23, 42, 0.8);
    border-left: 4px solid var(--accent);
    padding: 15px 20px;
    border-radius: 8px;
    margin-bottom: 15px;
}

.tutor-card h4 {
    color: var(--accent);
    margin-bottom: 8px;
    font-size: 1.1rem;
}

.tutor-card p {
    color: var(--text-main);
    line-height: 1.5;
    font-size: 0.95rem;
    margin-bottom: 0;
}

/* Good/Bad Report Blocks */
.report-section {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    margin-bottom: 20px;
}
.good-box, .bad-box {
    flex: 1;
    min-width: 200px;
    background: rgba(15, 23, 42, 0.8);
    padding: 15px 20px;
    border-radius: 8px;
}
.good-box {
    border-left: 4px solid var(--success);
}
.bad-box {
    border-left: 4px solid var(--danger);
}
.good-box h4, .bad-box h4 {
    margin-bottom: 8px;
    font-size: 1.1rem;
}
.good-box p, .bad-box p {
    color: var(--text-main);
    font-size: 0.95rem;
    line-height: 1.5;
}

/* In-quiz student explanation */
.explanation-box {
    margin-top: 20px;
    padding: 15px 20px;
    border-radius: 12px;
    background: rgba(15, 23, 42, 0.6);
    border-left: 4px solid var(--text-muted);
    animation: fadeIn 0.4s ease;
}

.explanation-box h4 {
    margin-bottom: 8px;
    font-size: 1.1rem;
}

.explanation-box.correct-exp {
    border-left-color: var(--success);
}
.explanation-box.correct-exp h4 {
    color: var(--success);
}

.explanation-box.wrong-exp {
    border-left-color: var(--danger);
}
.explanation-box.wrong-exp h4 {
    color: var(--danger);
}

.explanation-box p {
    color: var(--text-main);
    line-height: 1.5;
    font-size: 0.95rem;
}