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

body {
    font-family: 'Inter', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
    line-height: 1.6;
}

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

/* Header */
.header {
    text-align: center;
    margin-bottom: 40px;
    color: white;
}

.header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    text-shadow: 0 2px 4px rgba(0,0,0,0.3);
}

.header p {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* Main Content */
.main-content {
    display: grid;
    gap: 30px;
}

/* Sections */
section {
    background: white;
    border-radius: 20px;
    padding: 30px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

section:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px rgba(0,0,0,0.15);
}

section h2 {
    color: #4a5568;
    margin-bottom: 20px;
    font-size: 1.5rem;
    font-weight: 600;
    border-bottom: 3px solid #667eea;
    padding-bottom: 10px;
}

/* Input Section */
.number-input-container {
    display: flex;
    gap: 15px;
    align-items: center;
    flex-wrap: wrap;
}

#numberInput {
    flex: 1;
    min-width: 200px;
    padding: 15px 20px;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    outline: none;
}

#numberInput:focus {
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

/* Buttons */
.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    display: inline-block;
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-secondary {
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    color: white;
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(240, 147, 251, 0.4);
}

.btn-success {
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    color: white;
}

.btn-success:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(79, 172, 254, 0.4);
}

.btn-outline {
    background: transparent;
    color: #667eea;
    border: 2px solid #667eea;
}

.btn-outline:hover {
    background: #667eea;
    color: white;
    transform: translateY(-2px);
}

/* Number Display */
.number-display {
    text-align: center;
    margin-bottom: 30px;
}

.number-display .number {
    font-size: 3rem;
    font-weight: 700;
    color: #667eea;
    text-shadow: 0 2px 4px rgba(102, 126, 234, 0.2);
}

/* Digits Grid */
.digits-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 15px;
    margin-bottom: 30px;
}

.digit-card {
    background: linear-gradient(135deg, #f7fafc 0%, #edf2f7 100%);
    border: 2px solid #e2e8f0;
    border-radius: 15px;
    padding: 20px;
    text-align: center;
    transition: all 0.3s ease;
}

.digit-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.1);
    border-color: #667eea;
}

.digit-card .digit {
    font-size: 2rem;
    font-weight: 700;
    color: #667eea;
    margin-bottom: 8px;
}

.digit-card .position {
    font-size: 0.9rem;
    color: #718096;
    font-weight: 500;
    margin-bottom: 5px;
}

.digit-card .value {
    font-size: 0.8rem;
    color: #a0aec0;
    font-weight: 400;
}

/* Explanation */
.explanation {
    background: linear-gradient(135deg, #e6fffa 0%, #b2f5ea 100%);
    border-radius: 15px;
    padding: 20px;
    border-left: 5px solid #38b2ac;
}

.explanation h3 {
    color: #2d3748;
    margin-bottom: 10px;
    font-size: 1.2rem;
}

.explanation p {
    color: #4a5568;
    margin-bottom: 8px;
}

/* Practice Section */
.practice-controls {
    display: flex;
    gap: 15px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.practice-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: #667eea;
    text-align: center;
    margin: 20px 0;
    padding: 20px;
    background: linear-gradient(135deg, #f7fafc 0%, #edf2f7 100%);
    border-radius: 15px;
    border: 2px solid #e2e8f0;
}

.practice-inputs {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 15px;
    margin: 20px 0;
}

.practice-input {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.practice-input label {
    font-weight: 500;
    color: #4a5568;
    font-size: 0.9rem;
}

.practice-input input {
    padding: 10px 15px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.practice-input input:focus {
    border-color: #667eea;
    outline: none;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.result {
    margin-top: 20px;
    padding: 15px;
    border-radius: 10px;
    font-weight: 500;
}

.result.correct {
    background: linear-gradient(135deg, #c6f6d5 0%, #9ae6b4 100%);
    color: #22543d;
    border: 2px solid #68d391;
}

.result.incorrect {
    background: linear-gradient(135deg, #fed7d7 0%, #feb2b2 100%);
    color: #742a2a;
    border: 2px solid #fc8181;
}

/* Theory Section */
.theory-content {
    display: grid;
    gap: 20px;
}

.theory-card {
    background: linear-gradient(135deg, #f7fafc 0%, #edf2f7 100%);
    border-radius: 15px;
    padding: 20px;
    border-left: 5px solid #667eea;
}

.theory-card h3 {
    color: #2d3748;
    margin-bottom: 15px;
    font-size: 1.2rem;
    font-weight: 600;
}

.theory-card p {
    color: #4a5568;
    margin-bottom: 10px;
}

.theory-card ul {
    list-style: none;
    padding-left: 0;
}

.theory-card li {
    color: #4a5568;
    margin-bottom: 8px;
    padding-left: 20px;
    position: relative;
}

.theory-card li:before {
    content: "•";
    color: #667eea;
    font-weight: bold;
    position: absolute;
    left: 0;
}

/* Footer */
.footer {
    text-align: center;
    margin-top: 40px;
    color: white;
    opacity: 0.8;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }
    
    .header h1 {
        font-size: 2rem;
    }
    
    .number-input-container {
        flex-direction: column;
        align-items: stretch;
    }
    
    .practice-controls {
        flex-direction: column;
    }
    
    .digits-grid {
        grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    }
    
    .practice-inputs {
        grid-template-columns: 1fr;
    }
}

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

.analysis-section {
    animation: fadeIn 0.5s ease-out;
}

.digit-card {
    animation: fadeIn 0.3s ease-out;
}

/* Loading animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid #f3f3f3;
    border-top: 3px solid #667eea;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}