:root {
    --bg-primary: #0f172a;
    --bg-card: #1e293b;
    --bg-input: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: #475569;
    --accent-primary: #3b82f6;
    --accent-secondary: #8b5cf6;
    --error-color: #ef4444;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --gradient-primary: linear-gradient(135deg, #8014e6 0%, #673fc4 100%);
    --gradient-success: linear-gradient(135deg, #10b981 0%, #059669 100%);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

.custom-scrollbar::-webkit-scrollbar {
    width: 8px;
}

.custom-scrollbar::-webkit-scrollbar-track {
    background: var(--bg-card);
    border-radius: 4px;
}

.custom-scrollbar::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.custom-scrollbar::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

.step {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.4s ease-out, transform 0.4s ease-out;
    display: none;
}

.step.active {
    display: block;
    opacity: 1;
    transform: translateY(0);
}

.card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 2rem;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.3), 0 10px 10px -5px rgba(0, 0, 0, 0.2);
    backdrop-filter: blur(10px);
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    border: none;
    padding: 0.875rem 2rem;
    border-radius: 0.75rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px -1px rgba(59, 130, 246, 0.2), 0 2px 4px -1px rgba(59, 130, 246, 0.1);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    min-width: 160px;
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 10px 15px -3px rgba(162, 0, 255, 0.3), 0 4px 6px -2px rgba(59, 130, 246, 0.2);
}

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    filter: grayscale(100%);
}

#start-btn {
    min-width: unset;
    width: auto;
}

.btn-secondary {
    background: transparent;
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
    padding: 0.875rem 2rem;
    border-radius: 0.75rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.btn-secondary:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
    background: rgba(59, 130, 246, 0.1);
}

.back-btn {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 0.5rem;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.back-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    transform: translateX(-2px);
}

.input-field {
    width: 100%;
    background: var(--bg-input);
    border: 2px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.75rem 1rem;
    border-radius: 0.5rem;
    font-size: 1rem;
    transition: all 0.3s ease;
    outline: none;
}

.input-field:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.input-field.valid {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.05);
}

.input-field.invalid {
    border-color: var(--error-color);
    background: rgba(239, 68, 68, 0.05);
    animation: shake 0.4s ease-in-out;
}

.module-card {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    border-radius: 0.75rem;
    padding: 1.25rem;
    transition: all 0.3s ease;
}

#modules-container { padding: 4px; }

.module-card:hover {
    border-color: var(--accent-primary);
    background: rgba(255, 255, 255, 0.05);
    transform: translateY(-2px);
}

.module-title {
    font-weight: 700;
    color: var(--accent-secondary);
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.input-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.input-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
}

.module-input {
    width: 100%;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem;
    border-radius: 0.375rem;
    font-size: 0.95rem;
    transition: all 0.2s ease;
}

.module-input:focus {
    outline: none;
    border-color: var(--accent-primary);
}

.module-input.valid {
    border-color: var(--success-color);
}

.module-input.invalid {
    border-color: var(--error-color);
}

.error-text {
    color: var(--error-color);
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.text-primary {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.result-container {
    background: linear-gradient(135deg, rgba(59, 130, 246, 0.1) 0%, rgba(139, 92, 246, 0.1) 100%);
    border: 2px solid rgba(59, 130, 246, 0.3);
    border-radius: 1rem;
    padding: 2rem;
    position: relative;
    overflow: hidden;
}

.result-container::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: linear-gradient(45deg, transparent, rgba(59, 130, 246, 0.1), transparent);
    transform: rotate(45deg);
    animation: shimmer 3s infinite;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

@keyframes shimmer {
    0% { transform: translateX(-100%) rotate(45deg); }
    100% { transform: translateX(100%) rotate(45deg); }
}

@keyframes fade-in-down {
    0% {
        opacity: 0;
        transform: translateY(-20px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}

.animate-fade-in-down {
    animation: fade-in-down 0.6s ease-out;
}

@media (max-width: 640px) {
    .card {
        padding: 1.5rem;
    }
    
    .input-row {
        grid-template-columns: 1fr;
    }
    
    .result-container {
        padding: 1.5rem;
    }
    
    #final-grade {
        font-size: 3rem;
    }
}

@media (max-width: 768px) {
    #modules-container {
        max-height: 50vh;
    }
}