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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #f5f5f5 0%, #fff 50%, #e8f5e9 100%);
    min-height: 100vh;
    color: #333;
}

/* Header */
header {
    background: linear-gradient(135deg, #ff9800 0%, #ff5722 100%);
    color: white;
    padding: 20px;
    text-align: center;
    box-shadow: 0 4px 15px rgba(255, 152, 0, 0.4);
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
}

.lego-logo {
    height: 50px;
    filter: brightness(10);
}

h1 {
    font-size: 2.5em;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

h1 span {
    font-size: 0.6em;
    display: block;
    font-weight: 300;
}

.author {
    margin-top: 10px;
    font-size: 0.9em;
    opacity: 0.9;
}

/* Navigation Tabs */
.tabs {
    display: flex;
    justify-content: center;
    gap: 10px;
    padding: 20px;
    background: white;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.tab {
    padding: 12px 30px;
    border: none;
    border-radius: 25px;
    background: #e0e0e0;
    color: #666;
    font-size: 1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.tab:hover {
    background: #ffcc80;
    color: #e65100;
}

.tab.active {
    background: linear-gradient(135deg, #4caf50 0%, #81c784 100%);
    color: white;
    box-shadow: 0 4px 15px rgba(76, 175, 80, 0.4);
}

/* Main Content */
main {
    max-width: 900px;
    margin: 30px auto;
    padding: 0 20px;
}

.content {
    display: none;
}

.content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

/* Welcome Section */
.welcome {
    background: white;
    padding: 30px;
    border-radius: 20px;
    text-align: center;
    margin-bottom: 30px;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    border-left: 5px solid #ff9800;
}

.welcome h2 {
    color: #2e7d32;
    margin-bottom: 15px;
}

/* Feature Cards */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
}

.feature-card {
    background: white;
    padding: 25px;
    border-radius: 15px;
    text-align: center;
    box-shadow: 0 5px 20px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0,0,0,0.15);
}

.icon {
    font-size: 3em;
    margin-bottom: 15px;
}

.feature-card h3 {
    color: #ff5722;
    margin-bottom: 10px;
}

/* Folders */
.folder {
    background: white;
    border-radius: 15px;
    margin-bottom: 15px;
    box-shadow: 0 3px 15px rgba(0,0,0,0.1);
    overflow: hidden;
}

.folder-header {
    display: flex;
    align-items: center;
    padding: 18px 20px;
    cursor: pointer;
    background: linear-gradient(135deg, #fff 0%, #f5f5f5 100%);
    transition: background 0.3s ease;
}

.folder-header:hover {
    background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%);
}

.folder-icon {
    font-size: 1.5em;
    margin-right: 15px;
}

.folder-title {
    flex: 1;
    font-weight: 600;
    font-size: 1.1em;
    color: #333;
}

.folder-arrow {
    color: #ff9800;
    transition: transform 0.3s ease;
}

.folder.open .folder-arrow {
    transform: rotate(180deg);
}

.folder-content {
    display: none;
    padding: 0 20px 20px;
    background: linear-gradient(180deg, #f9f9f9 0%, #fff 100%);
}

.folder.open .folder-content {
    display: block;
    animation: slideDown 0.3s ease;
}

@keyframes slideDown {
    from { opacity: 0; max-height: 0; }
    to { opacity: 1; max-height: 1000px; }
}

/* Block Cards */
.block-card {
    padding: 20px;
    border-radius: 12px;
    margin: 10px 0;
    border-left: 5px solid;
}

.block-card.green {
    background: linear-gradient(135deg, #e8f5e9 0%, #c8e6c9 100%);
    border-color: #4caf50;
}

.block-card.orange {
    background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%);
    border-color: #ff9800;
}

.block-card.white {
    background: linear-gradient(135deg, #fafafa 0%, #f5f5f5 100%);
    border-color: #9e9e9e;
}

.block-card h4 {
    color: #333;
    margin-bottom: 10px;
}

.block-card .tip {
    margin-top: 15px;
    padding: 10px;
    background: rgba(255,255,255,0.7);
    border-radius: 8px;
    font-style: italic;
}

/* Combo Flow */
.combo-flow {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
    margin: 15px 0;
    padding: 15px;
    background: linear-gradient(135deg, #e3f2fd 0%, #bbdefb 100%);
    border-radius: 12px;
}

.combo-step {
    padding: 12px 18px;
    border-radius: 25px;
    font-weight: 600;
    color: white;
    box-shadow: 0 3px 10px rgba(0,0,0,0.2);
}

.combo-step.green {
    background: linear-gradient(135deg, #4caf50 0%, #81c784 100%);
}

.combo-step.orange {
    background: linear-gradient(135deg, #ff9800 0%, #ffb74d 100%);
}

.combo-arrow {
    font-size: 1.5em;
    color: #666;
}

.combo-list {
    list-style: none;
    padding: 15px;
    background: rgba(255,255,255,0.8);
    border-radius: 10px;
    margin: 10px 0;
}

.combo-list li {
    padding: 8px 0;
    border-bottom: 1px solid #eee;
}

.combo-list li:last-child {
    border-bottom: none;
}

.combo-desc {
    margin-top: 15px;
    padding: 15px;
    background: white;
    border-radius: 10px;
    color: #555;
    font-style: italic;
}

/* Tips */
.folder-content p {
    padding: 15px;
    background: linear-gradient(135deg, #fff 0%, #f5f5f5 100%);
    border-radius: 10px;
    line-height: 1.6;
}

/* Footer */
footer {
    background: linear-gradient(135deg, #4caf50 0%, #2e7d32 100%);
    color: white;
    text-align: center;
    padding: 20px;
    margin-top: 50px;
}

/* Responsive */
@media (max-width: 600px) {
    h1 {
        font-size: 1.8em;
    }
    
    .tabs {
        flex-wrap: wrap;
    }
    
    .tab {
        padding: 10px 20px;
        font-size: 0.9em;
    }
    
    .combo-flow {
        flex-direction: column;
        align-items: stretch;
    }
    
    .combo-arrow {
        transform: rotate(90deg);
        text-align: center;
    }
}