:root {
    --primary-color: #2c3e50;
    --accent-blue: #3498db;
    --accent-red: #e74c3c;
    --bg-color: #f4f7f6;
    --card-bg: #ffffff;
    --text-color: #333333;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

/* Header */
header {
    background: linear-gradient(135deg, var(--primary-color), #1a252f);
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

/* Tab Navigation */
.tab-menu {
    display: flex;
    justify-content: center;
    background-color: var(--card-bg);
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
    flex-wrap: wrap;
    position: sticky;
    top: 0;
    z-index: 100;
}

.tab-btn {
    background: none;
    border: none;
    padding: 15px 20px;
    font-size: 1rem;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
    border-bottom: 3px solid transparent;
    color: var(--primary-color);
}

.tab-btn:hover {
    background-color: #ecf0f1;
}

.tab-btn.active {
    border-bottom: 3px solid var(--accent-blue);
    color: var(--accent-blue);
}

/* Content Sections */
main {
    max-width: 900px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.tab-content {
    display: none;
    animation: fadeIn 0.4s;
}

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

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

h2 {
    color: var(--primary-color);
    border-bottom: 2px solid var(--accent-blue);
    padding-bottom: 10px;
    margin-bottom: 20px;
}

/* Cards & Layouts */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    margin-bottom: 20px;
}

.card {
    background-color: var(--card-bg);
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    border-left: 4px solid var(--accent-blue);
}

.card h3 {
    margin-bottom: 10px;
    color: var(--primary-color);
}

.highlight-ussr {
    border-left: 4px solid var(--accent-red);
}

/* Bullet Lists */
.bullet-list {
    list-style-type: none;
    padding-left: 0;
}

.bullet-list li {
    background-color: var(--card-bg);
    margin-bottom: 10px;
    padding: 15px;
    border-radius: 5px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    border-left: 4px solid var(--primary-color);
}

/* Info Box */
.info-box {
    background-color: #ffeaa7;
    color: #d35400;
    padding: 15px;
    border-radius: 5px;
    margin-bottom: 20px;
    border-left: 4px solid #f39c12;
}

/* Timeline */
.timeline {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}

.timeline ul {
    list-style: none;
    border-left: 3px solid var(--accent-blue);
    padding-left: 20px;
    margin-left: 10px;
}

.timeline li {
    margin-bottom: 15px;
    position: relative;
}

.timeline li::before {
    content: '';
    position: absolute;
    left: -28px;
    top: 5px;
    width: 12px;
    height: 12px;
    background-color: var(--accent-red);
    border-radius: 50%;
}

/* Aufgaben Section */
.task-box {
    background-color: var(--card-bg);
    padding: 25px;
    border-radius: 8px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
    margin-bottom: 25px;
    border: 1px solid #e0e0e0;
}

.task-type {
    display: inline-block;
    background-color: var(--primary-color);
    color: white;
    padding: 3px 8px;
    border-radius: 4px;
    font-size: 0.8rem;
    margin-bottom: 10px;
}

.task-box h3 {
    margin-bottom: 15px;
}

.solution-btn {
    background-color: var(--accent-blue);
    color: white;
    border: none;
    padding: 10px 15px;
    border-radius: 5px;
    cursor: pointer;
    font-weight: bold;
    margin-top: 15px;
    transition: background 0.3s;
}

.solution-btn:hover {
    background-color: #2980b9;
}

.solution-content {
    display: none;
    margin-top: 15px;
    padding: 15px;
    background-color: #e8f4f8;
    border-left: 4px solid var(--accent-blue);
    border-radius: 4px;
}

.solution-content.show {
    display: block;
}

/* Footer */
footer {
    text-align: center;
    padding: 20px;
    margin-top: 40px;
    background-color: var(--primary-color);
    color: white;
}