* {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    margin: 0;
    padding: 1rem;
    background-color: #f5f5f5;
    color: #333;
}

section {
    background: white;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

h1 {
    margin: 1.5rem 0 1rem 0;
    font-size: 1.3rem;
    color: #2c3e50;
    border-bottom: 2px solid #3498db;
    padding-bottom: 0.5rem;
}

h1:first-of-type {
    margin-top: 0;
}

label {
    display: block;
    margin-top: 0.8rem;
    margin-bottom: 0.3rem;
    font-weight: 600;
    font-size: 0.9rem;
    color: #2c3e50;
}

input, select {
    padding: 0.6rem;
    font-size: 1rem;
    width: 100%;
    border: 1px solid #bdc3c7;
    border-radius: 4px;
    transition: border-color 0.2s;
}

input:focus, select:focus {
    outline: none;
    border-color: #3498db;
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.result {
    margin-top: 0.8rem;
    padding: 0.8rem;
    background-color: #ecf0f1;
    border-left: 4px solid #3498db;
    border-radius: 4px;
    font-weight: bold;
    color: #2c3e50;
    min-height: 50px;
    display: flex;
    align-items: center;
}

/* Mobile-first: 1 column */
.grid-4col {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

/* Tablet (768px and up): 2 columns */
@media (min-width: 768px) {
    body {
        padding: 1.5rem;
    }

    section {
        padding: 2rem;
    }

    .grid-4col {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Desktop (1024px and up): 4 columns or flex layout */
@media (min-width: 1024px) {
    body {
        display: flex;
        gap: 2rem;
        max-width: 1400px;
        margin: 0 auto;
        padding: 2rem;
    }

    section {
        flex: 1;
    }

    .grid-4col {
        grid-template-columns: repeat(4, 1fr);
    }
}