:root {
    /* Light Mode Variables */
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    
    --bg: #f3f4f6;
    --card-bg: #ffffff;
    --card-border: #cbd5e1;
    --card-shadow: rgba(0, 0, 0, 0.05);
    
    --text: #1f2937;
    --text-light: #6b7280;
    --heading-border: #e5e7eb;
    
    --success: #10b981;
    --danger: #ef4444;
    
    --header-bg: #ffffff;
    --btn-hover: #f3f4f6;
    --option-bg: #ffffff;
    --option-hover: #f9fafb;
    --option-selected-bg: #eef2ff;
    
    --review-bg: #ffffff;
    --exp-bg: #eff6ff;
    --exp-text: #1e3a8a;
}

body.dark-mode {
    /* Dark Mode Variables */
    --primary: #6366f1;
    --primary-hover: #818cf8;
    
    --bg: #111827;
    --card-bg: #1f2937;
    --card-border: #374151;
    --card-shadow: rgba(0, 0, 0, 0.3);
    
    --text: #f9fafb;
    --text-light: #9ca3af;
    --heading-border: #374151;
    
    --header-bg: #1f2937;
    --btn-hover: #374151;
    --option-bg: #1f2937;
    --option-hover: #374151;
    --option-selected-bg: #312e81;
    
    --review-bg: #1f2937;
    --exp-bg: #1e293b;
    --exp-text: #bfdbfe;
}

/* --- Global Reset & Layout --- */
body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg);
    color: var(--text);
    margin: 0;
    padding: 0;
    transition: background-color 0.3s, color 0.3s;
    /* Flexbox for Sticky Footer support */
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

main {
    max-width: 800px;
    width: 100%;
    margin: 30px auto;
    padding: 0 20px;
    /* Important: Extra padding at bottom so content isn't hidden behind footer */
    padding-bottom: 80px !important; 
    flex: 1; 
    box-sizing: border-box;
}

.hidden {
    display: none !important;
}

/* --- Header --- */
header {
    background: var(--header-bg);
    border-bottom: 1px solid var(--heading-border);
    padding: 0.8rem 1.5rem;
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background-color 0.3s;
}

.header-content {
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 15px;
}

h1 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text);
    margin: 0;
}

h2 {
    color: var(--text);
    font-size: 1.5rem;
    margin-bottom: 20px;
    border-bottom: 2px solid var(--primary);
    padding-bottom: 10px;
}

/* --- Buttons --- */
.nav-btn {
    background: transparent;
    border: 1px solid var(--card-border);
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s;
    color: var(--text);
}

.nav-btn:hover {
    background: var(--btn-hover);
    border-color: var(--text-light);
}

.primary-btn, .success-btn, .secondary-btn {
    padding: 12px 24px;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    transition: all 0.2s ease;
    text-align: center;
    width: 100%; 
}

.primary-btn {
    background: var(--primary);
    color: white;
    border: 2px solid var(--primary);
}

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

.success-btn {
    background: var(--success);
    color: white;
    border: 2px solid var(--success);
}

.success-btn:hover {
    background: #059669;
    border-color: #059669;
}

.secondary-btn {
    background: var(--card-bg);
    border: 2px solid var(--card-border);
    color: var(--text);
}

.secondary-btn:hover {
    background: var(--btn-hover);
    border-color: var(--text-light);
}

/* --- Cards --- */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 20px;
}

.card {
    background: var(--card-bg);
    padding: 25px;
    border-radius: 12px;
    box-shadow: 0 4px 6px var(--card-shadow);
    cursor: pointer;
    transition: all 0.2s;
    border: 1px solid var(--card-border);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.15);
    border-color: var(--primary);
    background-color: var(--option-hover);
}

.card h3 {
    margin: 10px 0 5px;
    font-size: 1.1rem;
    color: var(--text);
}

.card p {
    color: var(--text-light);
    font-size: 0.9rem;
    margin: 0;
}

.icon {
    font-size: 2rem;
    margin-bottom: 10px;
}

/* Card Specific Hover Colors */
.syllabus-card-bg:hover {
    border-color: #3b82f6;
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

.practice-card-bg:hover {
    border-color: #10b981;
    box-shadow: 0 0 0 2px rgba(16, 185, 129, 0.2);
}

.summary-card-bg:hover {
    border-color: #f97316;
    box-shadow: 0 0 0 2px rgba(249, 115, 22, 0.2);
}

/* --- Syllabus View --- */
.syllabus-box {
    background: var(--card-bg);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 1px 3px var(--card-shadow);
    border: 1px solid var(--card-border);
}

.syllabus-module {
    margin-bottom: 25px;
    padding-bottom: 15px;
    border-bottom: 1px solid var(--heading-border);
}

.syllabus-module:last-child {
    border-bottom: none;
}

.syllabus-module h4 {
    color: var(--primary);
    margin: 0 0 10px 0;
    font-size: 1.1rem;
}

.syllabus-module ul {
    margin: 0;
    padding-left: 20px;
    color: var(--text-light);
    line-height: 1.6;
}

/* --- Quiz UI --- */
.quiz-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 20px;
    font-weight: 600;
    color: var(--text-light);
}

.question-box {
    background: var(--card-bg);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 4px 6px -1px var(--card-shadow);
    border: 1px solid var(--card-border);
}

#question-text {
    color: var(--text);
}

.options-grid.locked {
    pointer-events: none;
    opacity: 0.9;
}

.option-btn {
    width: 100%;
    padding: 15px;
    margin-bottom: 10px;
    border: 2px solid var(--card-border);
    background: var(--option-bg);
    color: var(--text);
    border-radius: 8px;
    text-align: left;
    cursor: pointer;
    font-size: 1rem;
    transition: 0.2s;
}

.option-btn:hover {
    border-color: var(--text-light);
    background: var(--option-hover);
}

.option-btn.selected {
    border-color: var(--primary);
    background: var(--option-selected-bg);
    color: var(--primary);
    font-weight: 600;
}

.option-btn.correct-immediate {
    background-color: #d1fae5;
    border-color: var(--success);
    color: #065f46;
    font-weight: 600;
}

.option-btn.wrong-immediate {
    background-color: #fee2e2;
    border-color: var(--danger);
    color: #991b1b;
}

.quiz-footer {
    display: flex;
    justify-content: space-between;
    gap: 15px;
    margin-top: 20px;
}

.quiz-footer button {
    flex: 1;
    width: auto;
    min-width: 0;
}

/* --- Results View --- */
.result-summary {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

.score-card {
    background: var(--card-bg);
    padding: 30px;
    border-radius: 16px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-width: 160px;
    box-shadow: 0 4px 6px -1px var(--card-shadow);
    border: 1px solid var(--card-border);
    flex: 1;
    max-width: 300px;
}

.score-label {
    text-transform: uppercase;
    letter-spacing: 1px;
    font-size: 0.8rem;
    color: var(--text-light);
    font-weight: 600;
}

#score-text, #time-text {
    font-size: 3.5rem;
    margin: 10px 0;
    color: var(--primary);
}

#score-percentage {
    font-size: 1.2rem;
    color: var(--text-light);
    font-weight: 500;
}

.review-list {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.review-item {
    background: var(--review-bg);
    padding: 20px;
    border-radius: 10px;
    border: 1px solid var(--card-border);
    border-left: 5px solid #ccc;
    box-shadow: 0 1px 2px var(--card-shadow);
    color: var(--text);
}

.review-item.correct {
    border-left-color: var(--success);
}

.review-item.wrong {
    border-left-color: var(--danger);
}

.review-q {
    font-weight: 600;
    margin-bottom: 10px;
    display: block;
    color: var(--text);
}

.review-detail {
    font-size: 0.95rem;
    margin: 5px 0;
}

.val-correct {
    color: var(--success);
    font-weight: 600;
}

.val-wrong {
    color: var(--danger);
    font-weight: 600;
    text-decoration: line-through;
    margin-right: 10px;
}

.explanation {
    margin-top: 10px;
    padding-top: 10px;
    border-top: 1px dashed var(--heading-border);
    font-size: 0.9rem;
    color: var(--text-light);
    font-style: italic;
}

.result-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    margin-top: 30px;
}

/* --- Study Mode --- */
.summary-item {
    background: var(--card-bg);
    padding: 25px;
    border-radius: 12px;
    box-shadow: 0 2px 4px var(--card-shadow);
    border: 1px solid var(--card-border);
    margin-bottom: 20px;
}

.summary-q {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 15px;
    display: block;
}

.summary-answer {
    background-color: rgba(16, 185, 129, 0.1);
    border: 1px solid var(--success);
    color: var(--success);
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 15px;
    font-size: 1rem;
    font-weight: 600;
}

.summary-explanation {
    padding: 15px;
    background-color: var(--exp-bg);
    border-left: 4px solid var(--primary);
    border-radius: 4px;
    font-size: 0.95rem;
    color: var(--exp-text);
    font-style: italic;
}

.summary-controls {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 25px;
}

.toggle-btn {
    padding: 10px 20px;
    border: 2px solid var(--card-border);
    background: var(--card-bg);
    color: var(--text-light);
    border-radius: 25px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.2s ease;
    font-size: 0.95rem;
}

.toggle-btn:hover {
    background: var(--btn-hover);
    transform: translateY(-2px);
}

.toggle-btn.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    box-shadow: 0 4px 6px rgba(79, 70, 229, 0.2);
}

.explanation-only-card {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 12px;
    box-shadow: 0 2px 4px var(--card-shadow);
    border: 1px solid var(--card-border);
    border-left: 5px solid #8b5cf6;
    margin-bottom: 15px;
    display: flex;
    gap: 15px;
    align-items: flex-start;
}

.exp-number {
    background: #8b5cf6;
    color: white;
    font-weight: bold;
    padding: 8px 12px;
    border-radius: 8px;
    font-size: 0.9rem;
    min-width: 35px;
    text-align: center;
    box-shadow: 0 2px 4px rgba(139, 92, 246, 0.3);
}

.exp-text {
    color: var(--text);
    line-height: 1.6;
    font-size: 1rem;
    margin-top: 4px;
}

/* --- Floating Footer --- */
footer {
    position: fixed;       
    bottom: 0;
    left: 0;
    width: 100%;            
    background: var(--header-bg); 
    border-top: 1px solid var(--heading-border);
    padding: 15px 0;
    text-align: center;
    z-index: 1000;          
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.1); 
    backdrop-filter: blur(5px); 
}

footer p {
    margin: 0;
    color: var(--text-light);
    font-size: 0.9rem;
}

footer a {
    color: var(--primary);
    text-decoration: none;
    font-weight: 700;
    transition: color 0.2s;
}

footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}