/* ============================================================================
   CSS Variables - Colors, Spacing, Typography
   ============================================================================ */

:root {
    /* Colors - Light Theme */
    --color-primary: #2563eb;
    --color-primary-dark: #1e40af;
    --color-primary-light: #3b82f6;
    --color-background: #ffffff;
    --color-surface: #f8fafc;
    --color-surface-alt: #f1f5f9;
    --color-input-bg: #fffbeb;
    --color-output-bg: #ecfdf5;
    --color-border: #e2e8f0;
    --color-border-dark: #cbd5e1;
    --color-warning: #f59e0b;
    --color-warning-light: #fef3c7;
    --color-error: #ef4444;
    --color-error-light: #fee2e2;
    --color-success: #10b981;
    --color-text: #1e293b;
    --color-text-muted: #64748b;
    --color-text-light: #94a3b8;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --line-height-tight: 1.3;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;

    /* Touch target minimum */
    --touch-min: 44px;

    /* Border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
}

/* ============================================================================
   Global Styles
   ============================================================================ */

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--color-text);
    background-color: var(--color-background);
}

/* ============================================================================
   Typography
   ============================================================================ */

h1 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    line-height: var(--line-height-tight);
    margin-bottom: var(--space-xs);
}

h2 {
    font-size: var(--font-size-xl);
    font-weight: 600;
    line-height: var(--line-height-tight);
    margin-bottom: var(--space-md);
    color: var(--color-text);
}

h3 {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

p {
    margin-bottom: var(--space-md);
}

small, .small {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* ============================================================================
   Layout - Mobile First
   ============================================================================ */

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.app-header {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
    color: white;
    padding: var(--space-lg);
    text-align: center;
    box-shadow: var(--shadow-md);
}

.app-header h1 {
    color: white;
    margin-bottom: var(--space-sm);
}

.subtitle {
    font-size: var(--font-size-sm);
    opacity: 0.95;
    margin: 0;
}

main {
    flex: 1;
    padding: var(--space-sm);
    max-width: 1280px;
    width: 100%;
    margin: 0 auto;
}

.app-layout {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

/* ============================================================================
   Section Styling
   ============================================================================ */

.compound-selector-section,
.composition-section {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    box-shadow: var(--shadow-sm);
}

.composition-section {
    background: white;
}

/* ============================================================================
   Search and Filter Controls
   ============================================================================ */

.search-controls {
    margin-bottom: var(--space-lg);
}

.search-input-group {
    margin-bottom: var(--space-md);
}

.search-input {
    width: 100%;
    padding: var(--space-md);
    font-size: var(--font-size-base);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-input-bg);
    color: var(--color-text);
    transition: border-color var(--transition-fast);
}

.search-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.search-hint {
    display: block;
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-top: var(--space-sm);
}

.filter-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.filter-group label {
    font-weight: 600;
    font-size: var(--font-size-sm);
    color: var(--color-text);
}

.category-filter {
    padding: var(--space-sm) var(--space-md);
    font-size: var(--font-size-base);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-input-bg);
    color: var(--color-text);
    cursor: pointer;
    transition: border-color var(--transition-fast);
    min-height: var(--touch-min);
}

.category-filter:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ============================================================================
   Search Results
   ============================================================================ */

.search-results-container {
    max-height: 400px;
    overflow-y: auto;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: white;
}

.results-placeholder {
    padding: var(--space-lg);
    text-align: center;
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
}

.search-result-item {
    padding: var(--space-md);
    border-bottom: 1px solid var(--color-border);
    cursor: pointer;
    transition: background-color var(--transition-fast);
    min-height: var(--touch-min);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

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

.search-result-item:hover {
    background-color: var(--color-surface-alt);
}

.search-result-item:active {
    background-color: var(--color-output-bg);
}

.result-name {
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--space-xs);
}

.result-formula {
    font-family: var(--font-mono);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

.result-properties {
    font-size: var(--font-size-sm);
    color: var(--color-text-light);
    margin-top: var(--space-xs);
}

/* ============================================================================
   Basis Toggle Controls
   ============================================================================ */

.basis-controls {
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--color-border);
}

.basis-controls h2 {
    margin-bottom: var(--space-md);
}

.basis-toggle {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    flex-wrap: wrap;
}

.basis-toggle label {
    font-weight: 600;
    font-size: var(--font-size-sm);
}

.toggle-group {
    display: flex;
    gap: 0;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-surface);
}

.basis-btn {
    flex: 1;
    min-width: 100px;
    padding: var(--space-sm) var(--space-md);
    font-size: var(--font-size-sm);
    font-weight: 600;
    border: none;
    background-color: transparent;
    color: var(--color-text-muted);
    cursor: pointer;
    transition: all var(--transition-fast);
    min-height: var(--touch-min);
}

.basis-btn:first-child {
    border-right: 1px solid var(--color-border);
}

.basis-btn:hover {
    background-color: var(--color-surface-alt);
    color: var(--color-text);
}

.basis-btn.basis-active {
    background-color: var(--color-primary);
    color: white;
    border: none;
}

/* ============================================================================
   Preset Controls
   ============================================================================ */

.preset-controls {
    margin-bottom: var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.preset-controls label {
    font-weight: 600;
    font-size: var(--font-size-sm);
}

.preset-selector {
    padding: var(--space-sm) var(--space-md);
    font-size: var(--font-size-base);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-input-bg);
    color: var(--color-text);
    cursor: pointer;
    transition: border-color var(--transition-fast);
    min-height: var(--touch-min);
}

.preset-selector:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

/* ============================================================================
   Composition Table
   ============================================================================ */

.composition-list-wrapper {
    margin-bottom: var(--space-lg);
    overflow-x: auto;
}

.composition-table {
    width: 100%;
    border-collapse: collapse;
    font-size: var(--font-size-sm);
}

.composition-table thead {
    background-color: var(--color-surface);
    border-bottom: 2px solid var(--color-border-dark);
}

.composition-table th {
    padding: var(--space-md);
    text-align: left;
    font-weight: 600;
    color: var(--color-text);
    white-space: nowrap;
}

.composition-table td {
    padding: var(--space-md);
    border-bottom: 1px solid var(--color-border);
}

.composition-table tbody tr {
    transition: background-color var(--transition-fast);
}

.composition-table tbody tr:hover {
    background-color: var(--color-surface-alt);
}

.input-header {
    background-color: #fefce8;
    color: #854d0e;
}

.converted-header {
    background-color: #ecfdf5;
    color: #065f46;
}

.composition-table input[type="number"],
.composition-table input[type="text"][inputmode="decimal"] {
    width: 100%;
    min-width: 90px;
    padding: var(--space-sm) var(--space-md);
    font-size: var(--font-size-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    background-color: var(--color-input-bg);
    color: var(--color-text);
    text-align: center;
    font-weight: 600;
    letter-spacing: 0.5px;
}

.composition-table input[type="number"]:focus,
.composition-table input[type="text"][inputmode="decimal"]:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.1);
}

.composition-table .properties {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    text-align: right;
}

.composition-table .actions {
    text-align: center;
}

.remove-btn {
    width: var(--touch-min);
    height: var(--touch-min);
    min-width: var(--touch-min);
    padding: 0;
    border: 1px solid var(--color-error);
    border-radius: var(--radius-md);
    background-color: white;
    color: var(--color-error);
    font-size: var(--font-size-lg);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.remove-btn:hover {
    background-color: var(--color-error-light);
    border-color: var(--color-error);
}

.remove-btn:active {
    background-color: var(--color-error);
    color: white;
}

.empty-state {
    padding: var(--space-xl);
    text-align: center;
    color: var(--color-text-muted);
    font-size: var(--font-size-sm);
    display: none;
}

.empty-state.visible {
    display: block;
}

/* ============================================================================
   Composition Footer
   ============================================================================ */

.composition-footer {
    padding: var(--space-md);
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-lg);
}

.total-display {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    justify-content: space-between;
}

.total-label {
    font-weight: 600;
    color: var(--color-text);
}

.total-value {
    font-size: var(--font-size-lg);
    font-weight: 700;
    color: var(--color-primary);
    font-family: var(--font-mono);
}

.total-status {
    font-size: var(--font-size-sm);
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-sm);
    display: none;
}

.total-status.warning {
    display: inline-block;
    background-color: var(--color-warning-light);
    color: #92400e;
}

.total-status.valid {
    display: inline-block;
    background-color: #d1fae5;
    color: #065f46;
}

/* ============================================================================
   Stream Properties Section
   ============================================================================ */

.stream-properties-section {
    background-color: var(--color-output-bg);
    border: 1px solid #a7f3d0;
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
}

.stream-properties-section h2 {
    color: #065f46;
    margin-bottom: var(--space-lg);
}

.properties-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-lg);
    margin-bottom: var(--space-lg);
}

.property-card {
    background-color: white;
    border: 1px solid #a7f3d0;
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    text-align: center;
}

.property-label {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-bottom: var(--space-sm);
    font-weight: 600;
}

.property-value {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: #065f46;
    font-family: var(--font-mono);
    margin-bottom: var(--space-xs);
}

.property-unit {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

.standard-conditions-note {
    padding: var(--space-md);
    background-color: white;
    border-left: 3px solid #10b981;
    border-radius: var(--radius-sm);
    color: var(--color-text-muted);
}

/* ============================================================================
   Tablet Breakpoint (640px)
   ============================================================================ */

@media (min-width: 640px) {
    main {
        padding: var(--space-md);
    }

    .app-header {
        padding: var(--space-xl);
    }

    .app-header h1 {
        font-size: 2rem;
    }

    .compound-selector-section,
    .composition-section {
        padding: var(--space-xl);
    }

    .filter-group {
        flex-direction: row;
        align-items: center;
    }

    .filter-group label {
        flex-shrink: 0;
    }

    .category-filter {
        flex: 1;
        min-width: 200px;
    }

    .basis-toggle {
        flex-wrap: nowrap;
    }

    .composition-table {
        font-size: var(--font-size-base);
    }

    .composition-table th,
    .composition-table td {
        padding: var(--space-md) var(--space-lg);
    }

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

    .property-card {
        padding: var(--space-xl);
    }
}

/* ============================================================================
   Desktop Breakpoint (1024px)
   ============================================================================ */

@media (min-width: 1024px) {
    .app-layout {
        flex-direction: row;
        gap: var(--space-xl);
        align-items: flex-start;
    }

    .compound-selector-section {
        flex: 0 0 40%;
        height: fit-content;
        position: sticky;
        top: var(--space-md);
    }

    .composition-section {
        flex: 1;
    }

    .search-results-container {
        max-height: 500px;
    }

    .composition-table {
        font-size: var(--font-size-base);
    }

    .properties-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

/* ============================================================================
   Print Styles
   ============================================================================ */

@media print {
    .app-header,
    .search-controls,
    .basis-toggle,
    .preset-controls,
    .composition-footer,
    .remove-btn {
        display: none;
    }

    body {
        background-color: white;
    }

    .composition-table {
        page-break-inside: avoid;
    }
}

/* ============================================================================
   Accessibility & Focus Visible
   ============================================================================ */

:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: more) {
    :root {
        --color-border: #000;
        --color-border-dark: #000;
    }

    .search-result-item {
        border: 1px solid #000;
    }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Animations */
@keyframes slideIn {
    from {
        transform: translateX(400px);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

/* Smooth transitions for status updates */
.total-status {
    transition: all var(--transition-normal);
}

.composition-table tbody tr {
    animation: fadeIn var(--transition-normal);
}