:root {
    --bg-color: #f4f7f6;
    --container-bg: #ffffff;
    --text-color: #333;
    --accent-color: #007bff;
    --accent-hover: #0056b3;
    --border-color: #ddd;
    --heading-color: #222;
    --muted-color: #666;
    --result-bg: #e9f5ff;
    --container-shadow: 0 4px 12px rgba(0,0,0,0.1);
    --container-padding: 2rem;
    --chart-bg: #ffffff;
    --btn-text: #ffffff;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #121212;
        --container-bg: #1e1e1e;
        --text-color: #e0e0e0;
        --accent-color: #3794ff;
        --accent-hover: #60a9ff;
        --border-color: #333;
        --heading-color: #ffffff;
        --muted-color: #bbb;
        --result-bg: #1a2633;
        --chart-bg: #2a2a2a;
        --btn-text: #ffffff;
    }
}

* {
    box-sizing: border-box;
    margin-top: 0px;
}

a {
    text-decoration: none;
    color: var(--accent-color);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    margin: 0;
    padding: 20px;
    display: flex;
    flex-direction: column; /* Ensure vertical stacking for flex children */
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.container {
    background-color: var(--container-bg);
    padding: var(--container-padding);
    border-radius: 12px;
    box-shadow: var(--container-shadow);
    width: 100%;
    max-width: 800px;
    margin: 20px auto;
}

h1, p.subtitle {
    text-align: center;
}

h1 {
    margin-bottom: 0.5rem;
    color: var(--heading-color);
}

p.subtitle {
    margin-bottom: 1.5rem;
    color: var(--muted-color);
}

.calculator {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-bottom: 1.5rem;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

label {
    display: block;
    font-weight: 600;
    font-size: 0.85rem;
    white-space: nowrap;
}

input[type="number"], select, input[type="text"], textarea {
    width: 100%;
    padding: 10px;
    background-color: var(--container-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

input:focus, select:focus, textarea:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(0,123,255,0.2);
}

/* Button Styles */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    border: none;
    transition: all 0.2s ease;
    background-color: var(--accent-color);
    color: var(--btn-text);
    text-decoration: none;
    line-height: 1.2;
}

.btn:hover {
    background-color: var(--accent-hover);
    transform: translateY(-1px);
    text-decoration: none;
}

.btn:active {
    transform: translateY(0);
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

.btn-small {
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
    border-radius: 4px;
}

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-color);
}

.btn-outline:hover {
    background-color: var(--border-color);
}

.result {
    padding: 1.2rem;
    background-color: var(--result-bg);
    border-radius: 8px;
    border-left: 4px solid var(--accent-color);
    text-align: left;
    margin-bottom: 2rem;
}

.result h3 {
    margin-top: 0;
    margin-bottom: 1rem;
    color: var(--heading-color);
    font-size: 1.1rem;
    text-align: center;
}

.total-payment {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin: 1rem 0;
    color: var(--accent-color);
}

.breakdown-item {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.breakdown-item:last-child {
    border-bottom: none;
}

.chart-section {
    margin-top: 2rem;
    height: 350px;
    position: relative;
    /* Added margin-bottom to create breathing room above footer */
    margin-bottom: 4rem;
}

.chart-section h3 {
    text-align: center;
    margin-bottom: 1rem;
}

/* About Section Global Styling */
.about-section {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 2px solid var(--border-color);
    text-align: left;
}

.about-section h2 {
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--heading-color);
    text-align: center;
}

.about-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

.about-item h4 {
    margin-bottom: 0.5rem;
    color: var(--accent-color);
    font-size: 1.1rem;
}

.about-item p {
    font-size: 0.95rem;
    color: var(--muted-color);
    margin: 0;
    text-align: left;
}

footer {
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
    margin-top: 2rem;
    text-align: center;
    color: var(--muted-color);
    font-size: 0.85rem;
    width: 100%; /* Ensure footer spans correctly in flex */
}

.footer-links {
    margin-top: 10px;
}
.footer-links a {
    color: var(--muted-color);
    text-decoration: none;
    margin: 0 10px;
}
.footer-links a:hover {
    text-decoration: underline;
}

/* Ensure spacing if multiple sections are present */
.hash-output-container, .verify-container {
    margin-bottom: 2rem;
}

@media (min-width: 601px) {
    .about-grid {
        grid-template-columns: 1fr 1fr;
    }
    .about-item.full-width {
        grid-column: span 2;
    }
}

@media (max-width: 600px) {
    body {
        padding: 0;
        display: block;
    }
    .container {
        padding: 1.5rem;
        box-shadow: none;
        border-radius: 0;
        min-height: 100vh;
        max-width: none;
        margin: 0;
    }
    .calculator {
        grid-template-columns: 1fr;
    }
    .total-payment {
        font-size: 2rem;
    }
    .chart-section {
        height: 250px;
        margin-bottom: 3rem;
    }
}