:root {
    --primary: #2c3e50;
    --secondary: #3498db;
    --accent: #e74c3c;
    --light: #ecf0f1;
    --dark: #2c3e50;
    --success: #2ecc71;
    --warning: #f39c12;
    --gray: #95a5a6;
}

.gravel-calculator-container {
    max-width: 1000px;
    margin: 30px auto;
    background: white;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    overflow: hidden;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.calculator-header {
    background: var(--primary);
    color: white;
    padding: 25px;
    text-align: center;
}

.calculator-header h2 {
    font-size: 28px;
    margin-bottom: 10px;
}

.calculator-header p {
    font-size: 16px;
    opacity: 0.9;
}

.calculator-body {
    display: flex;
    flex-wrap: wrap;
    padding: 0;
}

.input-section {
    flex: 1;
    min-width: 300px;
    padding: 30px;
    background: #f9f9f9;
}

.result-section {
    flex: 1;
    min-width: 300px;
    padding: 30px;
    background: var(--light);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

.input-group {
    margin-bottom: 20px;
}

.input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--dark);
}

.input-field {
    width: 100%;
    padding: 14px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 16px;
    transition: border-color 0.3s;
}

.input-field:focus {
    border-color: var(--secondary);
    outline: none;
}

.unit-select {
    width: 100%;
    padding: 14px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 16px;
    background: white;
    cursor: pointer;
}

.calculate-btn {
    width: 100%;
    padding: 16px;
    background: var(--secondary);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s;
    margin-top: 10px;
}

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

.result-box {
    text-align: center;
    background: white;
    padding: 25px;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
    width: 100%;
    margin-bottom: 25px;
}

.result-title {
    font-size: 20px;
    color: var(--dark);
    margin-bottom: 15px;
}

.result-value {
    font-size: 42px;
    font-weight: 700;
    color: var(--secondary);
    margin: 10px 0;
}

.result-unit {
    font-size: 18px;
    color: var(--gray);
}

.materials-list {
    width: 100%;
}

.material-item {
    display: flex;
    justify-content: space-between;
    padding: 12px 0;
    border-bottom: 1px solid #eee;
}

.material-name {
    font-weight: 600;
}

.material-amount {
    color: var(--secondary);
    font-weight: 600;
}

.visualization {
    width: 100%;
    margin-top: 25px;
    text-align: center;
}

.visualization-title {
    font-size: 18px;
    margin-bottom: 15px;
    color: var(--dark);
    font-weight: 600;
}

.gravel-visual {
    width: 100%;
    height: 120px;
    background: linear-gradient(90deg, #a0a0a0, #808080, #606060);
    border-radius: 8px;
    position: relative;
    overflow: hidden;
}

.gravel-piece {
    position: absolute;
    background: #909090;
    border-radius: 50%;
}

@media (max-width: 768px) {
    .calculator-body {
        flex-direction: column;
    }
    
    .input-section, .result-section {
        width: 100%;
    }
}

.info-text {
    font-size: 14px;
    color: var(--gray);
    margin-top: 5px;
}