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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: #fff;
}

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

.header {
    text-align: center;
    margin-bottom: 30px;
    padding: 30px;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.header p {
    font-size: 1.2em;
    opacity: 0.9;
}

.progress-path {
    display: flex;
    justify-content: space-between;
    margin-bottom: 40px;
    position: relative;
}

.progress-line {
    position: absolute;
    top: 40px;
    left: 10%;
    width: 80%;
    height: 4px;
    background: rgba(255, 255, 255, 0.2);
    z-index: 0;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #4ade80, #fbbf24);
    transition: width 0.5s ease;
    width: 0%;
}

.tier-indicator {
    flex: 1;
    text-align: center;
    position: relative;
    z-index: 1;
}

.tier-circle {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    margin: 0 auto 15px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2em;
    background: rgba(255, 255, 255, 0.2);
    border: 3px solid rgba(255, 255, 255, 0.3);
    backdrop-filter: blur(10px);
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
}

.tier-circle.unlocked {
    background: linear-gradient(135deg, #4ade80, #22c55e);
    border-color: #4ade80;
    box-shadow: 0 0 20px rgba(74, 222, 128, 0.5);
}

.tier-circle.current {
    background: linear-gradient(135deg, #fbbf24, #f59e0b);
    border-color: #fbbf24;
    box-shadow: 0 0 30px rgba(251, 191, 36, 0.7);
    animation: pulse 2s infinite;
}

.tier-circle.locked {
    background: rgba(100, 100, 100, 0.3);
    border-color: rgba(255, 255, 255, 0.2);
    cursor: not-allowed;
    opacity: 0.6;
}

.tier-circle:not(.locked):hover {
    transform: scale(1.1);
}

.tier-label {
    font-size: 0.9em;
    font-weight: bold;
    opacity: 0.9;
}

.tier-status {
    font-size: 0.75em;
    margin-top: 5px;
    opacity: 0.7;
}

.lock-icon {
    position: absolute;
    bottom: -5px;
    right: -5px;
    background: rgba(0, 0, 0, 0.5);
    border-radius: 50%;
    width: 25px;
    height: 25px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.6em;
}

.content-area {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    padding: 40px;
    margin-bottom: 30px;
    min-height: 400px;
    animation: fadeIn 0.5s ease;
}

.tier-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid rgba(255, 255, 255, 0.3);
}

.tier-title {
    font-size: 2em;
    font-weight: bold;
}

.tier-badge {
    background: linear-gradient(135deg, #fbbf24, #f59e0b);
    padding: 10px 25px;
    border-radius: 25px;
    font-size: 0.9em;
    font-weight: bold;
    box-shadow: 0 5px 15px rgba(251, 191, 36, 0.4);
}

.content-section {
    margin-bottom: 30px;
}

.section-title {
    font-size: 1.3em;
    font-weight: bold;
    margin-bottom: 15px;
    color: #fbbf24;
}

.section-content {
    line-height: 1.8;
    opacity: 0.95;
}

.concept-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 15px;
    margin-top: 15px;
}

.concept-card {
    background: rgba(255, 255, 255, 0.15);
    padding: 20px;
    border-radius: 15px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: all 0.3s ease;
}

.concept-card:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

.concept-card h4 {
    font-size: 1.1em;
    margin-bottom: 10px;
    color: #4ade80;
}

.unlock-requirements {
    background: rgba(251, 191, 36, 0.2);
    border: 2px solid rgba(251, 191, 36, 0.5);
    border-radius: 15px;
    padding: 20px;
    margin-top: 30px;
}

.unlock-requirements h3 {
    font-size: 1.2em;
    margin-bottom: 15px;
    color: #fbbf24;
}

.requirement-item {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 10px 0;
    padding: 10px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
}

.requirement-check {
    width: 25px;
    height: 25px;
    border-radius: 50%;
    background: rgba(74, 222, 128, 0.3);
    border: 2px solid #4ade80;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.9em;
}

.action-buttons {
    display: flex;
    gap: 15px;
    margin-top: 30px;
    justify-content: center;
}

.action-btn {
    padding: 15px 40px;
    background: linear-gradient(135deg, #4ade80, #22c55e);
    border: none;
    border-radius: 25px;
    color: white;
    font-size: 1.1em;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 5px 15px rgba(74, 222, 128, 0.4);
}

.action-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(74, 222, 128, 0.6);
}

.action-btn:disabled {
    background: rgba(100, 100, 100, 0.5);
    cursor: not-allowed;
    box-shadow: none;
}

.navigation {
    display: flex;
    justify-content: space-between;
    gap: 15px;
    margin-top: 30px;
}

.nav-btn {
    padding: 15px 30px;
    background: rgba(255, 255, 255, 0.2);
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 15px;
    color: white;
    text-decoration: none;
    font-size: 1em;
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
}

.nav-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@media (max-width: 768px) {
    .progress-path {
        flex-wrap: wrap;
    }

    .tier-indicator {
        flex: 0 0 50%;
        margin-bottom: 20px;
    }

    .concept-list {
        grid-template-columns: 1fr;
    }
}