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

body {
    font-family: 'Noto Sans', -apple-system, sans-serif;
    background: #ffffff;
    color: #1a1a1a;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    padding: 40px 0;
    border-bottom: 2px solid #000;
    margin-bottom: 30px;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.subtitle {
    font-size: 1.1rem;
    color: #666;
}

.tab-nav {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    border-bottom: 1px solid #ddd;
}

.tab-btn {
    background: none;
    border: none;
    padding: 15px 25px;
    font-size: 1rem;
    cursor: pointer;
    border-bottom: 3px solid transparent;
    transition: all 0.2s;
    font-weight: 500;
}

.tab-btn:hover {
    background: #f5f5f5;
}

.tab-btn.active {
    border-bottom-color: #000;
}

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

.tab-content.active {
    display: block;
}

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

h2 {
    font-size: 2rem;
    margin-bottom: 30px;
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
}

.skill-card {
    border: 2px solid #000;
    padding: 25px;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
}

.skill-card:hover {
    transform: translateY(-4px);
    box-shadow: 4px 4px 0 #000;
}

.skill-card.completed {
    background: #f0f0f0;
}

.skill-card h3 {
    font-size: 1.3rem;
    margin-bottom: 10px;
}

.skill-card p {
    color: #666;
    margin-bottom: 15px;
}

.skill-tag {
    display: inline-block;
    background: #000;
    color: #fff;
    padding: 4px 12px;
    font-size: 0.85rem;
    margin-right: 5px;
    margin-top: 5px;
}

.courses-container {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.course-card {
    border: 2px solid #000;
    padding: 30px;
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 20px;
}

.course-card h3 {
    font-size: 1.5rem;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: #e0e0e0;
    margin: 15px 0;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: #000;
    transition: width 0.3s;
}

.lesson-list {
    list-style: none;
    margin-top: 20px;
}

.lesson-item {
    padding: 12px;
    border-left: 3px solid #ddd;
    margin-bottom: 10px;
    cursor: pointer;
    transition: all 0.2s;
}

.lesson-item:hover {
    border-left-color: #000;
    background: #f5f5f5;
}

.lesson-item.completed {
    border-left-color: #000;
}

.lesson-item.completed::before {
    content: "✓ ";
    font-weight: bold;
}

.practice-area {
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 30px;
}

.exercise-selector {
    border-right: 2px solid #000;
    padding-right: 30px;
}

.exercise-btn {
    display: block;
    width: 100%;
    text-align: left;
    background: #fff;
    border: 2px solid #000;
    padding: 15px;
    margin-bottom: 10px;
    cursor: pointer;
    transition: all 0.2s;
}

.exercise-btn:hover {
    background: #000;
    color: #fff;
}

.exercise-btn.active {
    background: #000;
    color: #fff;
}

.exercise-workspace {
    min-height: 400px;
}

.placeholder {
    color: #999;
    text-align: center;
    padding: 100px 20px;
}

.exercise-content h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.exercise-content p {
    margin-bottom: 20px;
    color: #666;
}

textarea {
    width: 100%;
    min-height: 200px;
    padding: 15px;
    border: 2px solid #000;
    font-family: 'Noto Sans', sans-serif;
    font-size: 1rem;
    resize: vertical;
}

button.primary {
    background: #000;
    color: #fff;
    border: none;
    padding: 12px 30px;
    font-size: 1rem;
    cursor: pointer;
    margin-top: 15px;
    transition: transform 0.1s;
}

button.primary:hover {
    transform: scale(1.02);
}

button.primary:active {
    transform: scale(0.98);
}

.feedback {
    margin-top: 20px;
    padding: 20px;
    border: 2px solid #000;
    background: #f9f9f9;
}

.progress-dashboard {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
}

.stat-card {
    border: 2px solid #000;
    padding: 30px;
    text-align: center;
}

.stat-number {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.stat-label {
    color: #666;
    font-size: 1rem;
}

@media (max-width: 768px) {
    h1 {
        font-size: 1.8rem;
    }

    .tab-nav {
        flex-wrap: wrap;
    }

    .practice-area {
        grid-template-columns: 1fr;
    }

    .exercise-selector {
        border-right: none;
        border-bottom: 2px solid #000;
        padding-right: 0;
        padding-bottom: 20px;
        margin-bottom: 20px;
    }

    .skills-grid {
        grid-template-columns: 1fr;
    }
}