@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* Minimalist Monochromatic Design Tokens */
:root {
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;

    /* Light Mode Tokens */
    --bg-primary: #ffffff;
    --bg-secondary: #f4f4f5; /* Zinc 100 */
    --bg-card: #ffffff;
    --border-color: #e4e4e7; /* Zinc 200 */
    --border-focus: #09090b; /* Zinc 950 */
    
    --text-primary: #09090b;
    --text-secondary: #71717a; /* Zinc 500 */
    --text-muted: #a1a1aa; /* Zinc 400 */
    
    --accent: #09090b;
    --accent-hover: #27272a; /* Zinc 800 */
    --accent-light: #f4f4f5;
    
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    
    --transition: 150ms cubic-bezier(0.16, 1, 0.3, 1);
    
    --max-width: 720px;
}

/* Dark Mode Tokens */
[data-theme="dark"] {
    --bg-primary: #09090b; /* Zinc 950 */
    --bg-secondary: #18181b; /* Zinc 900 */
    --bg-card: #09090b;
    --border-color: #27272a; /* Zinc 800 */
    --border-focus: #fafafa; /* Zinc 50 */
    
    --text-primary: #fafafa;
    --text-secondary: #a1a1aa; /* Zinc 400 */
    --text-muted: #52525b; /* Zinc 700 */
    
    --accent: #fafafa;
    --accent-hover: #e4e4e7; /* Zinc 200 */
    --accent-light: #18181b;
}

/* Resets */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-sans);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    line-height: 1.6;
    padding: 0 1.25rem;
    transition: background-color var(--transition), color var(--transition);
    -webkit-font-smoothing: antialiased;
}

/* Centered container layout */
.app-container {
    width: 100%;
    max-width: var(--max-width);
    display: flex;
    flex-direction: column;
    gap: 3rem;
    padding: 2rem 0 5rem 0;
}

/* Minimal Header */
header {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.logo-section {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.125rem;
    letter-spacing: -0.03em;
}

.logo-section span {
    font-weight: 400;
    color: var(--text-secondary);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

/* Minimal Toggler */
.theme-toggle {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    transition: background-color var(--transition);
}

.theme-toggle:hover {
    background-color: var(--bg-secondary);
}

.theme-toggle .fa-sun {
    display: none;
}

[data-theme="dark"] .theme-toggle .fa-moon {
    display: none;
}

[data-theme="dark"] .theme-toggle .fa-sun {
    display: block;
}

.btn-minimal {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.815rem;
    padding: 0.5rem 0.875rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.35rem;
    transition: all var(--transition);
}

.btn-minimal:hover {
    border-color: var(--border-focus);
    background-color: var(--bg-secondary);
}

.btn-primary {
    background-color: var(--accent);
    color: var(--bg-primary);
    font-weight: 600;
    font-size: 0.815rem;
    padding: 0.5rem 0.875rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--accent);
    cursor: pointer;
    transition: all var(--transition);
}

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

/* Minimal Title Section */
.hero-title {
    font-size: 1.75rem;
    font-weight: 800;
    letter-spacing: -0.04em;
    margin-bottom: 0.5rem;
    text-align: left;
}

.hero-description {
    font-size: 0.95rem;
    color: var(--text-secondary);
    font-weight: 400;
}

/* Card layout */
.minimal-card {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 2rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.card-title {
    font-size: 1rem;
    font-weight: 700;
    letter-spacing: -0.01em;
}

/* Category select list bar */
.category-wrapper {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.input-label {
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-secondary);
}

.select-wrapper {
    position: relative;
    width: 100%;
}

.custom-select {
    width: 100%;
    height: 42px;
    padding: 0 2.5rem 0 0.875rem;
    background-color: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-primary);
    appearance: none;
    cursor: pointer;
    outline: none;
    transition: border-color var(--transition);
}

.custom-select:focus {
    border-color: var(--border-focus);
}

.select-chevron {
    position: absolute;
    right: 0.875rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 0.75rem;
    pointer-events: none;
}

/* Converter Inputs Columns */
.converter-grid {
    display: grid;
    grid-template-columns: 1fr;
    align-items: center;
    gap: 1.25rem;
}

@media (min-width: 640px) {
    .converter-grid {
        grid-template-columns: 1fr auto 1fr;
    }
}

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

.value-input-wrapper {
    position: relative;
    border-bottom: 2px solid var(--border-color);
    transition: border-color var(--transition);
}

.value-input-wrapper:focus-within {
    border-color: var(--border-focus);
}

.value-input {
    width: 100%;
    height: 56px;
    padding: 0;
    background: none;
    border: none;
    font-size: 2.25rem;
    font-weight: 700;
    color: var(--text-primary);
    font-family: var(--font-sans);
    outline: none;
}

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

.value-input[readonly] {
    color: var(--text-secondary);
}

/* Search Dropdown Select Component */
.search-select-container {
    position: relative;
}

.search-select-btn {
    width: 100%;
    height: 38px;
    padding: 0 2rem 0 0.75rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.815rem;
    font-weight: 600;
    color: var(--text-primary);
    text-align: left;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
    outline: none;
    transition: border-color var(--transition);
}

.search-select-btn:hover, .search-select-btn:focus {
    border-color: var(--border-focus);
}

.search-select-dropdown {
    display: none;
    position: absolute;
    top: calc(100% + 4px);
    left: 0;
    width: 100%;
    background-color: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    z-index: 50;
    padding: 0.35rem;
}

[data-theme="dark"] .search-select-dropdown {
    box-shadow: 0 4px 12px rgba(0,0,0,0.5);
}

.search-select-dropdown.active {
    display: block;
}

.search-select-filter {
    width: 100%;
    height: 34px;
    padding: 0 0.5rem 0 1.75rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.815rem;
    color: var(--text-primary);
    margin-bottom: 0.35rem;
    outline: none;
}

.search-select-filter:focus {
    border-color: var(--border-focus);
}

.search-select-filter-icon {
    position: absolute;
    left: 0.875rem;
    top: 0.75rem;
    font-size: 0.75rem;
    color: var(--text-muted);
    pointer-events: none;
}

.search-select-options {
    max-height: 180px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
}

.search-select-option {
    padding: 0.35rem 0.5rem;
    font-size: 0.815rem;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.search-select-option:hover {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
}

.search-select-option.selected {
    background-color: var(--accent-light);
    color: var(--text-primary);
    font-weight: 600;
}

/* Swap Icon button */
.swap-btn-container {
    display: flex;
    justify-content: center;
}

.swap-btn {
    width: 36px;
    height: 36px;
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
}

.swap-btn:hover {
    border-color: var(--border-focus);
    transform: rotate(180deg);
}

/* Result detail text output footer */
.result-footer {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    padding-top: 1.25rem;
    border-top: 1px solid var(--border-color);
}

@media (min-width: 640px) {
    .result-footer {
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
    }
}

.result-detail-text {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.result-detail-text span {
    color: var(--text-primary);
    font-weight: 700;
}

.result-actions {
    display: flex;
    gap: 0.5rem;
}

/* References block list styling */
.reference-layout {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.formula-box {
    padding-bottom: 1.25rem;
    border-bottom: 1px solid var(--border-color);
}

.formula-math {
    font-family: var(--font-mono);
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.formula-description {
    font-size: 0.815rem;
    color: var(--text-secondary);
}

.table-container {
    overflow-x: auto;
    width: 100%;
}

.conversion-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.815rem;
    text-align: left;
}

.conversion-table th {
    font-weight: 700;
    color: var(--text-secondary);
    padding: 0.5rem 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.conversion-table td {
    padding: 0.5rem 0.75rem;
    color: var(--text-primary);
    border-bottom: 1px solid var(--border-color);
}

.conversion-table tr:hover td {
    background-color: var(--bg-secondary);
}

.conversion-table td.mono {
    font-family: var(--font-mono);
}

/* Collapsible module lists (Recent history / FAQs) */
.history-section {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.history-clear {
    background: none;
    border: none;
    font-size: 0.75rem;
    font-weight: 600;
    color: #ef4444;
    cursor: pointer;
    text-decoration: underline;
}

.history-list {
    list-style: none;
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.5rem;
}

@media (min-width: 640px) {
    .history-list {
        grid-template-columns: 1fr 1fr;
    }
}

.history-item {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-secondary);
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    transition: all var(--transition);
}

.history-item:hover {
    border-color: var(--border-focus);
    color: var(--text-primary);
}

.history-empty {
    grid-column: span 2;
    text-align: center;
    font-size: 0.815rem;
    color: var(--text-muted);
    font-style: italic;
    padding: 1rem 0;
}

/* FAQ Details/Summary */
.faq-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.faq-summary {
    padding: 0.875rem 1.25rem;
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    list-style: none;
}

.faq-summary::-webkit-details-marker {
    display: none;
}

.faq-summary i {
    font-size: 0.75rem;
    transition: transform var(--transition);
    color: var(--text-muted);
}

.faq-item[open] .faq-summary i {
    transform: rotate(180deg);
}

.faq-content {
    padding: 0 1.25rem 0.875rem 1.25rem;
    font-size: 0.815rem;
    color: var(--text-secondary);
}

/* Clean Constants Panel */
.constants-list {
    list-style: none;
    display: grid;
    grid-template-columns: 1fr;
    gap: 0.5rem;
}

@media (min-width: 640px) {
    .constants-list {
        grid-template-columns: 1fr 1fr;
    }
}

.constants-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.815rem;
    font-weight: 500;
    color: var(--text-secondary);
}

.constants-item i {
    color: var(--text-muted);
    font-size: 0.7rem;
}

/* Footer block list elements */
footer {
    border-top: 1px solid var(--border-color);
    padding-top: 2rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    align-items: center;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.footer-nav {
    display: flex;
    gap: 1.5rem;
}

.footer-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition);
}

.footer-link:hover {
    color: var(--text-primary);
}

/* Toast container alert styles */
.toast-container {
    position: fixed;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    background-color: var(--accent);
    color: var(--bg-primary);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    font-size: 0.75rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    opacity: 0;
    transform: translateY(10px);
    animation: slideUp 200ms ease forwards;
}

@keyframes slideUp {
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

/* Compliant Ad Container Styles */
.ad-section-container {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    margin: 1.5rem 0;
}

.ad-label {
    font-size: 0.65rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
}

.ad-slot-box {
    width: 100%;
    min-height: 90px;
    max-height: 280px;
    background-color: var(--bg-secondary);
    border: 1px dashed var(--border-color);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}