@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&display=swap');

:root {
    --primary: #6366f1;
    --primary-light: #818cf8;
    --primary-dark: #4f46e5;
    --bg-dark: #0f172a;
    --bg-card: #1e293b;
    --bg-hover: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border: #334155;
    --success: #10b981;
    --shadow: rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: var(--text-primary);
    min-height: 100vh;
    padding: 2rem;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 3rem;
    padding: 2rem;
    background: var(--bg-card);
    border-radius: 1rem;
    box-shadow: 0 4px 6px var(--shadow);
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Progress Bar */
.progress-bar {
    position: relative;
    width: 100%;
    height: 2rem;
    background: var(--bg-dark);
    border-radius: 1rem;
    overflow: hidden;
    box-shadow: inset 0 2px 4px var(--shadow);
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary) 0%, var(--primary-light) 100%);
    border-radius: 1rem;
    transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    width: 0%;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-weight: 600;
    font-size: 0.875rem;
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
}

/* Content */
.content {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Topic Sections */
.topic-section {
    background: var(--bg-card);
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 4px 6px var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

.topic-section:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 12px var(--shadow);
}

.topic-section > h2 {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--primary-light);
    border-bottom: 2px solid var(--border);
    padding-bottom: 0.75rem;
}

/* Subtopics */
.subtopic {
    margin-bottom: 2rem;
}

.subtopic:last-child {
    margin-bottom: 0;
}

.subtopic h3 {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.subtopic h3::before {
    content: "▸";
    color: var(--primary);
    font-size: 1.5rem;
}

/* Lists */
.subtopic ul {
    list-style: none;
    padding-left: 0;
}

.subtopic li {
    display: flex;
    align-items: center;
    padding: 0.75rem;
    margin-bottom: 0.5rem;
    background: var(--bg-dark);
    border-radius: 0.5rem;
    border: 1px solid transparent;
    transition: all 0.2s ease;
}

.subtopic li:hover {
    background: var(--bg-hover);
    border-color: var(--primary);
    transform: translateX(4px);
}

/* Checkboxes */
input[type="checkbox"] {
    appearance: none;
    width: 1.25rem;
    height: 1.25rem;
    border: 2px solid var(--border);
    border-radius: 0.25rem;
    margin-right: 0.75rem;
    cursor: pointer;
    position: relative;
    flex-shrink: 0;
    transition: all 0.2s ease;
}

input[type="checkbox"]:hover {
    border-color: var(--primary);
}

input[type="checkbox"]:checked {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    border-color: var(--primary);
}

input[type="checkbox"]:checked::after {
    content: "✓";
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 0.875rem;
    font-weight: bold;
}

input[type="checkbox"]:checked + label {
    text-decoration: line-through;
    opacity: 0.6;
}

/* Labels */
label {
    cursor: pointer;
    flex: 1;
    user-select: none;
    transition: opacity 0.2s ease;
}

/* Footer */
footer {
    text-align: center;
    margin-top: 3rem;
    padding: 1.5rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Responsive */
@media (max-width: 768px) {
    body {
        padding: 1rem;
    }

    h1 {
        font-size: 1.75rem;
    }

    .topic-section {
        padding: 1.5rem;
    }

    .topic-section > h2 {
        font-size: 1.5rem;
    }

    .subtopic h3 {
        font-size: 1.125rem;
    }
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.topic-section {
    animation: fadeIn 0.5s ease-out;
}

.topic-section:nth-child(1) { animation-delay: 0.1s; }
.topic-section:nth-child(2) { animation-delay: 0.2s; }
.topic-section:nth-child(3) { animation-delay: 0.3s; }
.topic-section:nth-child(4) { animation-delay: 0.4s; }
.topic-section:nth-child(5) { animation-delay: 0.5s; }
.topic-section:nth-child(6) { animation-delay: 0.6s; }
.topic-section:nth-child(7) { animation-delay: 0.7s; }
.topic-section:nth-child(8) { animation-delay: 0.8s; }

/* Scrollbar */
::-webkit-scrollbar {
    width: 10px;
}

::-webkit-scrollbar-track {
    background: var(--bg-dark);
}

::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: 5px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary-light);
}