:root {
    /* Nature Distilled Palette */
    --bg-color: #F9F8F4;
    /* Cloud Dancer */
    --card-bg: #E8E4DF;
    /* Clay/Stone */
    --text-color: #463F3A;
    /* Peat/Deep Charcoal */
    --accent-color: #6C7A45;
    /* Darker Sage for WCAG AA with white text */
    --accent-hover: #566137;
    /* Darker Sage Hover */
    --border-color: #A8A59E;
    /* Weathered Gray */
    --input-bg: #F2F0EB;
    /* Lighter Clay */
    --error-color: #8B4A4A;
    /* Darker Muted Red for contrast */

    /* Typography */
    --font-stack: 'Courier New', Courier, monospace;
}

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

body {
    background-color: var(--bg-color);
    /* Organic "Dappled Light" Background */
    background-image:
        radial-gradient(circle at 15% 50%, rgba(210, 207, 196, 0.4) 0%, transparent 25%),
        radial-gradient(circle at 85% 30%, rgba(138, 154, 91, 0.08) 0%, transparent 30%),
        radial-gradient(circle at 50% 80%, rgba(232, 228, 223, 0.6) 0%, transparent 40%);
    background-attachment: fixed;
    color: var(--text-color);
    font-family: var(--font-stack);
    line-height: 1.6;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

.calc-container {
    background-color: var(--card-bg);
    padding: 2rem;
    border: 1px solid var(--border-color);
    box-shadow: 10px 10px 20px rgba(0, 0, 0, 0.05), -5px -5px 15px rgba(255, 255, 255, 0.5);
    max-width: 400px;
    width: 100%;
    position: relative;
}

/* Subtle paper texture effect */
.calc-container::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: url("data:image/svg+xml,%3Csvg width='100' height='100' viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.8' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100' height='100' filter='url(%23noise)' opacity='0.05'/%3E%3C/svg%3E");
    pointer-events: none;
    z-index: 0;
}

.content-wrapper {
    position: relative;
    z-index: 1;
    /* Ensure content is above texture */
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

h1 {
    font-size: 1.5rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.5rem;
    margin-bottom: 0.5rem;
    text-align: center;
}

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

label {
    font-size: 0.9rem;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
}

input[type="number"],
select {
    background-color: var(--input-bg);
    border: none;
    border-bottom: 2px solid var(--border-color);
    padding: 0.8rem;
    padding-right: 2.5rem;
    /* Make room for spinners */
    font-family: var(--font-stack);
    font-size: 1rem;
    color: var(--text-color);
    transition: all 0.3s ease;
    width: 100%;
}

input[type="number"]:focus,
select:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
    border-bottom-color: var(--accent-color);
    background-color: #fff;
}

button {
    background-color: var(--accent-color);
    color: #fff;
    border: none;
    padding: 1rem;
    font-family: var(--font-stack);
    font-size: 1rem;
    text-transform: uppercase;
    letter-spacing: 2px;
    cursor: pointer;
    transition: background-color 0.3s ease;
    margin-top: 1rem;
    box-shadow: 2px 2px 5px rgba(0, 0, 0, 0.1);
}

button:focus {
    outline: 2px solid var(--text-color);
    outline-offset: 2px;
}

button:hover {
    background-color: var(--accent-hover);
}

.output-section {
    margin-top: 1rem;
    min-height: 80px;
    /* Reserve space for 2 lines of text roughly */
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    background-color: rgba(255, 255, 255, 0.4);
    border: 1px dashed var(--border-color);
    padding: 1rem;
    border-radius: 4px;
}

.result-success {
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--text-color);
}

.result-error {
    color: var(--error-color);
    font-weight: bold;
}

.back-link {
    display: block;
    text-align: center;
    margin-top: 1.5rem;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.8rem;
    opacity: 0.7;
    transition: opacity 0.3s ease;
}

.back-link:hover {
    opacity: 1;
    text-decoration: underline;
}

/* Custom Validation Styles */
.field-error {
    color: var(--error-color);
    font-size: 0.8rem;
    font-weight: bold;
    min-height: 1.2em;
    /* Reserve space or just let it expand */
    margin-top: 0.2rem;
}

.input-invalid {
    border-bottom-color: var(--error-color) !important;
}

/* Custom Select Styling */
.custom-select-wrapper {
    position: relative;
    user-select: none;
}

.custom-select {
    position: relative;
    font-family: var(--font-stack);
}

.select-selected {
    background-color: var(--input-bg);
    border-bottom: 2px solid var(--border-color);
    padding: 0.8rem;
    color: var(--text-color);
    cursor: pointer;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.select-selected:focus {
    outline: 2px solid var(--accent-color);
    outline-offset: 2px;
}

.select-selected:after {
    position: absolute;
    content: "";
    top: 1.2rem;
    right: 1rem;
    width: 0;
    height: 0;
    border: 6px solid transparent;
    border-color: var(--text-color) transparent transparent transparent;
}

.select-selected.select-arrow-active:after {
    border-color: transparent transparent var(--text-color) transparent;
    top: 0.8rem;
}

.select-items {
    position: absolute;
    background-color: #fff;
    /* Clean white for contrast */
    border: 1px solid var(--border-color);
    border-top: none;
    z-index: 99;
    top: 100%;
    left: 0;
    right: 0;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.select-items div {
    color: var(--text-color);
    padding: 0.8rem;
    cursor: pointer;
    border-bottom: 1px solid #eee;
    transition: background-color 0.2s;
}

.select-items div:last-child {
    border-bottom: none;
}

.select-items div:hover,
.select-items div:focus {
    background-color: var(--input-bg);
    outline: none;
    /* Custom background instead of outline for options, usually cleaner */
}

/* Add left border indicator for keyboard focus on items if preferred */
.select-items div:focus {
    border-left: 4px solid var(--accent-color);
    padding-left: calc(0.8rem - 4px);
}

.select-hide {
    display: none;
}

/* Custom Input Wrapper & Spinners */
.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

/* Hide default browser spinners */
input[type=number]::-webkit-inner-spin-button,
input[type=number]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    appearance: none;
    margin: 0;
}

input[type=number] {
    -moz-appearance: textfield;
    appearance: textfield;
    /* Firefox */
}

.spinner-controls {
    position: absolute;
    right: 5px;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.spinner-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 0.6rem;
    padding: 0;
    margin: 0;
    color: var(--text-color);
    box-shadow: none;
    opacity: 0.6;
    transition: opacity 0.2s;
    line-height: 1;
}

.spinner-btn:hover {
    opacity: 1;
    background: none;
    color: var(--accent-hover);
}

.spinner-btn:focus {
    outline: none;
    /* Removed outline for cleaner look, they are small targets */
}