/* styles.css - Modern & Beautiful Mobile Design */

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

/* Global Resets & Basics */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-tap-highlight-color: transparent;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

:root {
    /* Modern Vibrant Color Palette */
    --primary: #6366F1;
    --primary-light: #818CF8;
    --primary-dark: #4F46E5;
    --secondary: #EC4899;
    --secondary-light: #F472B6;
    --accent: #06B6D4;
    --accent-light: #22D3EE;
    --success: #10B981;
    --warning: #F59E0B;
    --error: #EF4444;
    
    /* Dark Mode Backgrounds */
    --bg-darkest: #0F0F1A;
    --bg-dark: #1A1A2E;
    --bg-medium: #252542;
    --bg-light: #2D2D4A;
    --bg-lighter: #363663;
    
    /* Text Colors */
    --text-header: #F8FAFC;
    --text-primary: #E2E8F0;
    --text-secondary: #94A3B8;
    --text-muted: #64748B;
    
    /* Spacing System */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 12px;
    --space-lg: 16px;
    --space-xl: 24px;
    --space-2xl: 32px;
    --space-3xl: 48px;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
    
    /* Modern Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3), 0 1px 3px 0 rgba(0, 0, 0, 0.15);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.15);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.35), 0 4px 6px -4px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 8px 10px -6px rgba(0, 0, 0, 0.15);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.3);
    --shadow-glow-pink: 0 0 20px rgba(236, 72, 153, 0.3);
    --shadow-glow-cyan: 0 0 20px rgba(6, 182, 212, 0.3);
    
    /* Transitions */
    --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-normal: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-bounce: 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* RGB Values */
    --primary-rgb: 99, 102, 241;
    --secondary-rgb: 236, 72, 153;
    --accent-rgb: 6, 182, 212;
    --success-rgb: 16, 185, 129;
}

/* Light Mode */
@media (prefers-color-scheme: light) {
    :root {
        --bg-darkest: #F1F5F9;
        --bg-dark: #FFFFFF;
        --bg-medium: #F8FAFC;
        --bg-light: #F1F5F9;
        --bg-lighter: #E2E8F0;
        
        --text-header: #1E293B;
        --text-primary: #334155;
        --text-secondary: #64748B;
        --text-muted: #94A3B8;
        
        --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05), 0 1px 3px 0 rgba(0, 0, 0, 0.05);
        --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
        --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.05);
        --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.12), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
    }
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-darkest);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Layout */
.container {
    width: 100%;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.main-content {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
    padding-bottom: calc(var(--space-3xl) + 34px);
    scrollbar-width: thin;
    scrollbar-color: var(--primary) transparent;
}

.main-content::-webkit-scrollbar {
    width: 6px;
}

.main-content::-webkit-scrollbar-track {
    background: transparent;
}

.main-content::-webkit-scrollbar-thumb {
    background: var(--primary);
    border-radius: var(--radius-full);
}

/* Header */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: linear-gradient(135deg, var(--bg-dark) 0%, var(--bg-medium) 100%);
    padding: max(44px, var(--space-md)) var(--space-lg) var(--space-lg);
    display: flex;
    align-items: center;
    gap: var(--space-md);
    border-bottom: 1px solid var(--bg-light);
    position: relative;
    overflow: hidden;
}

.header::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 300px;
    height: 300px;
    background: radial-gradient(circle, rgba(var(--primary-rgb), 0.15) 0%, transparent 70%);
    pointer-events: none;
}

.header::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -10%;
    width: 200px;
    height: 200px;
    background: radial-gradient(circle, rgba(var(--secondary-rgb), 0.1) 0%, transparent 70%);
    pointer-events: none;
}

.header-content {
    flex: 1;
    position: relative;
    z-index: 1;
}

.header h1 {
    font-family: 'Poppins', sans-serif;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--space-xs);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    color: var(--text-header);
    letter-spacing: -0.02em;
}

.header p {
    font-size: 0.85rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    color: var(--text-secondary);
}

.header-icon {
    font-size: 2rem;
    position: relative;
    z-index: 1;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: float 3s ease-in-out infinite;
    filter: drop-shadow(0 4px 8px rgba(var(--primary-rgb), 0.3));
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

/* Tabs Navigation */
.tabs-navigation {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--bg-dark);
    border-top: 1px solid var(--bg-light);
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: var(--space-xs);
    padding: var(--space-sm);
    padding-bottom: calc(var(--space-sm) + 34px);
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.3);
    z-index: 50;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.tab-btn {
    background: transparent;
    border: none;
    border-radius: var(--radius-md);
    padding: var(--space-sm);
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    font-size: 0.7rem;
    transition: all var(--transition-normal);
    font-weight: 500;
    text-align: center;
    position: relative;
}

.tab-btn:hover {
    color: var(--text-primary);
    background: var(--bg-light);
}

.tab-btn:active {
    transform: scale(0.92);
}

.tab-btn.active {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    box-shadow: var(--shadow-glow);
    font-weight: 600;
}

.tab-icon {
    font-size: 1.3rem;
    transition: transform var(--transition-bounce);
}

.tab-btn.active .tab-icon {
    transform: translateY(-2px);
}

.tab-badge {
    position: absolute;
    top: -4px;
    right: 4px;
    background: linear-gradient(135deg, var(--secondary), var(--error));
    color: white;
    font-size: 0.6rem;
    font-weight: 700;
    min-width: 18px;
    height: 18px;
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    animation: badgePop 0.4s var(--transition-bounce) forwards;
    border: 2px solid var(--bg-dark);
    box-shadow: var(--shadow-sm);
}

@keyframes badgePop {
    0% { transform: scale(0); opacity: 0; }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); opacity: 1; }
}

/* Search Section */
.search-section {
    padding: var(--space-lg);
    background: var(--bg-medium);
    border-bottom: 1px solid var(--bg-light);
    position: sticky;
    top: 0;
    z-index: 10;
}

.search-box {
    position: relative;
    display: flex;
    align-items: center;
    background: var(--bg-dark);
    border: 2px solid var(--bg-light);
    border-radius: var(--radius-full);
    padding: var(--space-sm) var(--space-lg);
    transition: all var(--transition-normal);
}

.search-box:focus-within {
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(var(--primary-rgb), 0.15), var(--shadow-glow);
}

.search-input {
    flex: 1;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 1rem;
    outline: none;
    padding: var(--space-xs) 0;
    font-family: 'Inter', sans-serif;
}

.search-input::placeholder {
    color: var(--text-muted);
}

.search-icon {
    font-size: 1.1rem;
    color: var(--primary);
    margin-right: var(--space-sm);
}

.search-clear {
    font-size: 1.1rem;
    color: var(--text-muted);
    cursor: pointer;
    margin-left: var(--space-sm);
    transition: all var(--transition-fast);
    padding: 4px;
    border-radius: var(--radius-full);
}

.search-clear:hover {
    background: var(--bg-light);
    color: var(--error);
}

.search-clear:active {
    transform: scale(0.9) rotate(90deg);
}

/* Categories List */
.categories-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-md);
    padding: var(--space-lg);
}

.category-item {
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: var(--space-lg);
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.category-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: linear-gradient(180deg, var(--primary) 0%, var(--secondary) 100%);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.category-item:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    border-color: rgba(var(--primary-rgb), 0.3);
}

.category-item:hover::before {
    opacity: 1;
}

.category-item:active {
    transform: scale(0.98);
}

.category-icon {
    font-size: 2.2rem;
    flex-shrink: 0;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    filter: drop-shadow(0 2px 4px rgba(var(--primary-rgb), 0.2));
}

.category-info {
    flex: 1;
    overflow: hidden;
}

.category-name {
    font-family: 'Poppins', sans-serif;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-header);
    margin-bottom: var(--space-xs);
}

.category-count {
    font-size: 0.8rem;
    color: var(--text-muted);
    background: var(--bg-dark);
    display: inline-block;
    padding: 4px 12px;
    border-radius: var(--radius-full);
    font-weight: 500;
}

/* Subcategories */
.subcategory-item {
    background: var(--bg-medium);
    border: 1px solid var(--bg-light);
    border-radius: var(--radius-md);
    padding: var(--space-md) var(--space-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    margin-bottom: var(--space-sm);
}

.subcategory-item::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 0;
    height: 100%;
    background: linear-gradient(90deg, rgba(var(--accent-rgb), 0.1), transparent);
    transition: width var(--transition-normal);
}

.subcategory-item:hover {
    background: var(--bg-light);
    transform: translateX(4px);
    border-color: var(--accent);
}

.subcategory-item:hover::after {
    width: 100%;
}

.subcategory-item:active {
    transform: translateX(0) scale(0.99);
}

.subcategory-name {
    font-weight: 600;
    color: var(--text-primary);
    position: relative;
    z-index: 1;
}

.count {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    padding: 6px 12px;
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    font-weight: 700;
    position: relative;
    z-index: 1;
    box-shadow: var(--shadow-sm);
}

/* Formula Cards */
.formulas-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-md);
    padding: var(--space-lg);
}

.formula-card {
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.formula-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--secondary), var(--accent));
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.formula-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    border-color: rgba(var(--primary-rgb), 0.3);
}

.formula-card:hover::before {
    opacity: 1;
}

.formula-card:active {
    transform: scale(0.98);
}

.formula-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--space-md);
}

.formula-title {
    font-family: 'Poppins', sans-serif;
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-header);
    flex: 1;
}

.formula-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

.formula-display {
    background: var(--bg-darkest);
    border: 1px solid var(--bg-light);
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    font-family: 'Fira Code', 'Courier New', monospace;
    font-size: 0.9rem;
    color: var(--accent-light);
    overflow-x: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.2);
}

.formula-button {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    border: none;
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    box-shadow: var(--shadow-md);
    font-family: 'Poppins', sans-serif;
}

.formula-button:hover {
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    transform: translateY(-1px);
}

.formula-button:active {
    transform: scale(0.97);
}

/* Favorite Button */
.fav-btn {
    background: none;
    border: none;
    font-size: 1.4rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    padding: var(--space-xs);
    color: var(--text-muted);
    position: relative;
}

.fav-btn:hover {
    color: var(--secondary);
    transform: scale(1.1);
}

.fav-btn:active {
    transform: scale(1.2);
}

.fav-btn.active {
    color: var(--secondary);
    filter: drop-shadow(0 0 8px rgba(var(--secondary-rgb), 0.5));
    animation: heartBeat 0.5s var(--transition-bounce);
}

@keyframes heartBeat {
    0%, 100% { transform: scale(1); }
    25% { transform: scale(1.3); }
    50% { transform: scale(1); }
    75% { transform: scale(1.15); }
}

/* Back Button */
.back-button-container {
    padding: var(--space-lg) var(--space-lg) 0;
}

.back-button {
    background: var(--bg-medium);
    color: var(--text-primary);
    border: 1px solid var(--bg-light);
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-full);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    box-shadow: var(--shadow-sm);
    font-family: 'Poppins', sans-serif;
}

.back-button:hover {
    background: var(--bg-light);
    transform: translateX(-4px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary);
}

.back-button:active {
    transform: translateX(-8px) scale(0.98);
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    align-items: flex-end;
    z-index: 1000;
    opacity: 1;
    transition: opacity var(--transition-normal);
    animation: fadeInModal var(--transition-normal) ease-out;
    backdrop-filter: blur(4px);
}

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

.modal.hidden {
    display: none;
    opacity: 0;
}

.modal-content {
    background: linear-gradient(180deg, var(--bg-dark) 0%, var(--bg-medium) 100%);
    width: 100%;
    max-height: 90vh;
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
    padding: var(--space-xl);
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    box-shadow: 0 -8px 40px rgba(0, 0, 0, 0.5);
    animation: slideUpContent var(--transition-normal) ease-out;
    border-top: 3px solid transparent;
    border-image: linear-gradient(90deg, var(--primary), var(--secondary)) 1;
    border-image-slice: 1 0 0 0;
}

@keyframes slideUpContent {
    from { transform: translateY(100%); }
    to { transform: translateY(0); }
}

.modal-close {
    position: absolute;
    top: var(--space-lg);
    right: var(--space-lg);
    background: linear-gradient(135deg, var(--error), var(--secondary));
    border: none;
    font-size: 1.2rem;
    color: white;
    cursor: pointer;
    transition: all var(--transition-fast);
    z-index: 10;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-md);
}

.modal-close:hover {
    transform: rotate(90deg) scale(1.1);
    box-shadow: var(--shadow-glow-pink);
}

/* Modal Body */
.modal-title {
    font-family: 'Poppins', sans-serif;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-header);
    margin-bottom: var(--space-md);
    padding-top: var(--space-lg);
    letter-spacing: -0.02em;
}

.modal-description {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-xl);
    line-height: 1.6;
}

.modal-section {
    margin-bottom: var(--space-2xl);
}

.modal-section-title {
    font-family: 'Poppins', sans-serif;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--accent);
    margin-bottom: var(--space-md);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--bg-light);
}

.modal-formula {
    background: var(--bg-darkest);
    border: 1px solid var(--bg-light);
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-lg);
    font-family: 'Fira Code', 'Courier New', monospace;
    font-size: 0.95rem;
    color: var(--accent-light);
    overflow-x: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.2);
}

/* Variables Input */
.variables-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-lg);
    margin-bottom: var(--space-xl);
}

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

.variable-label {
    font-family: 'Poppins', sans-serif;
    font-weight: 600;
    color: var(--text-header);
    font-size: 0.95rem;
}

.variable-input {
    width: 100%;
    padding: var(--space-md) var(--space-lg);
    background: var(--bg-dark);
    border: 2px solid var(--bg-light);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: 'Fira Code', monospace;
    transition: all var(--transition-fast);
}

.variable-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(var(--primary-rgb), 0.15), var(--shadow-glow);
}

.variable-input::placeholder {
    color: var(--text-muted);
}

.variable-unit {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* Calculate Button */
.calculate-button {
    width: 100%;
    padding: var(--space-lg) var(--space-xl);
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1.05rem;
    font-weight: 700;
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-md);
    margin: var(--space-xl) 0;
    box-shadow: var(--shadow-lg);
    font-family: 'Poppins', sans-serif;
    position: relative;
    overflow: hidden;
}

.calculate-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.6s;
}

.calculate-button:hover {
    box-shadow: var(--shadow-xl), var(--shadow-glow);
    transform: translateY(-2px);
}

.calculate-button:hover::before {
    left: 100%;
}

.calculate-button:active {
    transform: scale(0.97);
}

/* Result Box */
.result-box {
    background: linear-gradient(135deg, rgba(var(--success-rgb), 0.15) 0%, rgba(var(--accent-rgb), 0.1) 100%);
    border: 1px solid var(--success);
    padding: var(--space-xl);
    border-radius: var(--radius-lg);
    margin-top: var(--space-xl);
    animation: slideInResult 0.5s var(--transition-bounce);
    box-shadow: var(--shadow-lg), 0 0 20px rgba(var(--success-rgb), 0.2);
}

@keyframes slideInResult {
    from { opacity: 0; transform: translateY(20px) scale(0.95); }
    to { opacity: 1; transform: translateY(0) scale(1); }
}

.result-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: var(--space-sm);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 600;
}

.result-value {
    font-size: 2rem;
    font-weight: 800;
    color: var(--success);
    font-family: 'Fira Code', monospace;
    margin-bottom: var(--space-sm);
    word-break: break-all;
    text-shadow: 0 2px 8px rgba(var(--success-rgb), 0.3);
}

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

/* Recent Calculations */
.recent-list {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-md);
    padding: var(--space-lg);
}

.recent-calculation-item {
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    cursor: pointer;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-sm);
}

.recent-calculation-item:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--accent);
}

.recent-calculation-item:active {
    transform: scale(0.98);
}

.recent-header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-md);
}

.recent-title {
    font-family: 'Poppins', sans-serif;
    font-weight: 600;
    color: var(--text-header);
    font-size: 1rem;
    flex: 1;
}

.recent-delete-btn {
    background: none;
    border: none;
    font-size: 1.2rem;
    color: var(--text-muted);
    cursor: pointer;
    transition: all var(--transition-fast);
    padding: var(--space-xs);
    border-radius: var(--radius-full);
}

.recent-delete-btn:hover {
    background: rgba(var(--error-rgb), 0.1);
    color: var(--error);
}

.recent-delete-btn:active {
    transform: scale(1.2) rotate(90deg);
}

.recent-category {
    font-size: 0.8rem;
    color: var(--accent);
    margin-bottom: var(--space-xs);
    font-weight: 500;
}

.recent-time {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-bottom: var(--space-md);
}

.recent-result {
    background: var(--bg-darkest);
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-md);
    border-left: 3px solid var(--success);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.recent-result-value {
    color: var(--success);
    font-weight: 700;
    font-family: 'Fira Code', monospace;
    font-size: 1rem;
}

/* Clear Buttons */
.clear-btn {
    background: linear-gradient(135deg, var(--error), var(--secondary));
    color: white;
    border: none;
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-full);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    font-family: 'Poppins', sans-serif;
}

.clear-btn:hover {
    box-shadow: var(--shadow-lg), var(--shadow-glow-pink);
    transform: translateY(-1px);
}

.clear-btn:active {
    transform: scale(0.96);
}

/* Section Headers */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-lg);
    padding: var(--space-md) var(--space-lg) 0;
}

.section-header h2 {
    font-family: 'Poppins', sans-serif;
    color: var(--text-header);
    font-size: 1.3rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

/* Empty States */
.welcome-message,
.recent-empty,
.no-results,
.favorites-empty {
    text-align: center;
    padding: var(--space-3xl) var(--space-lg);
    color: var(--text-muted);
}

.empty-state-icon {
    font-size: 4rem;
    margin-bottom: var(--space-lg);
    animation: pulse 3s infinite ease-in-out;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    filter: drop-shadow(0 4px 8px rgba(var(--primary-rgb), 0.2));
}

@keyframes pulse {
    0%, 100% { transform: scale(1); opacity: 0.8; }
    50% { transform: scale(1.05); opacity: 1; }
}

.empty-state-text {
    font-family: 'Poppins', sans-serif;
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: var(--space-md);
}

/* Utilities */
.hidden {
    display: none !important;
}

.opacity-50 {
    opacity: 0.5;
}

.error {
    color: var(--error);
    font-weight: 600;
    font-size: 0.9rem;
    margin-top: var(--space-sm);
}

/* RGB Values */
:root {
    --error-rgb: 239, 68, 68;
}

/* Desktop Adjustments */
@media (min-width: 768px) {
    html {
        font-size: 15px;
    }

    body {
        display: flex;
        justify-content: center;
        align-items: flex-start;
        min-height: 100vh;
        background: linear-gradient(135deg, var(--bg-darkest) 0%, #1a1a3e 50%, var(--bg-dark) 100%);
    }

    .container {
        width: 100%;
        max-width: 420px;
        min-height: 90vh;
        max-height: 95vh;
        border-radius: var(--radius-xl);
        overflow: hidden;
        box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
        margin: var(--space-2xl) 0;
        border: 1px solid var(--bg-light);
    }

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

    .header h1 {
        font-size: 1.3rem;
    }

    .tabs-navigation {
        position: static;
        border-top: none;
        padding-bottom: var(--space-lg);
        background: transparent;
        backdrop-filter: none;
        box-shadow: none;
        margin-top: auto;
    }

    .main-content {
        padding-bottom: var(--space-lg);
    }

    .modal-content {
        max-height: 80vh;
        width: 90%;
        margin: 0 auto;
        border-radius: var(--radius-xl);
        position: relative;
        top: 5vh;
        animation: fadeInModal var(--transition-normal) ease-out, scaleInContent var(--transition-normal) ease-out;
    }

    @keyframes scaleInContent {
        from { opacity: 0; transform: scale(0.9); }
        to { opacity: 1; transform: scale(1); }
    }

    .modal {
        align-items: center;
    }

    .modal-close {
        top: var(--space-md);
        right: var(--space-md);
    }

    .search-section {
        border-radius: var(--radius-xl) var(--radius-xl) 0 0;
        overflow: hidden;
    }
}


/* =========================
   GRID COMPACT OVERRIDES
   (Keep original rules above for compatibility,
    these selectors target IDs used by the app and
    provide a compact grid presentation requested)
   ========================= */

/* Categories grid (for #categoriesContainer and fallback .categories-list) */
#categoriesContainer,
.categories-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: var(--space-md);
    padding: var(--space-lg);
}

#categoriesContainer .category-item,
.categories-list .category-item {
    /* Column-based compact card */
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 8px;
    text-align: center;
    padding: calc(var(--space-md) / 0.9);
    border-radius: var(--radius-md);
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
    min-height: 110px;
    overflow: hidden;
}

#categoriesContainer .category-item:hover,
.categories-list .category-item:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

#categoriesContainer .category-icon,
.categories-list .category-item .category-icon {
    font-size: 2.2rem;
    line-height: 1;
    flex-shrink: 0;
    margin: 4px 0;
}

#categoriesContainer .category-name,
.categories-list .category-item .category-name {
    font-family: 'Poppins', sans-serif;
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-header);
    margin: 0;
    white-space: nowrap;
    text-overflow: ellipsis;
    overflow: hidden;
    max-width: 100%;
}

#categoriesContainer .category-count,
.categories-list .category-item .category-count {
    font-size: 0.95rem;
    color: var(--text-muted);
    background: transparent;
    padding: 0;
    font-weight: 700;
    margin-top: 4px;
    display: inline-block;
}

/* Subcategories grid (for #subcategoriesContainer and fallback .subcategories-list) */
#subcategoriesContainer,
.subcategories-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
    gap: var(--space-sm);
    padding: var(--space-lg);
}

#subcategoriesContainer .subcategory-item,
.subcategories-list .subcategory-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 6px;
    text-align: center;
    padding: var(--space-md);
    border-radius: var(--radius-md);
    background: var(--bg-medium);
    border: 1px solid var(--bg-light);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
    min-height: 95px;
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

#subcategoriesContainer .subcategory-item:hover,
.subcategories-list .subcategory-item:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    border-color: var(--accent);
}

#subcategoriesContainer .subcategory-icon,
.subcategories-list .subcategory-item .subcategory-icon {
    font-size: 1.6rem;
    margin-bottom: 4px;
}

#subcategoriesContainer .subcategory-name,
.subcategories-list .subcategory-item .subcategory-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.95rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 100%;
}

#subcategoriesContainer .count,
.subcategories-list .subcategory-item .count {
    font-size: 0.9rem;
    background: none;
    color: var(--text-muted);
    padding: 0;
    font-weight: 700;
    margin-top: 6px;
}

/* Formulas grid (compact cards) */
#formulasContainer,
.formulas-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: var(--space-md);
    padding: var(--space-lg);
}

#formulasContainer .formula-card,
.formulas-list .formula-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-sm);
    text-align: center;
    padding: var(--space-md);
    min-height: 120px;
    border-radius: var(--radius-md);
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
    overflow: hidden;
}

#formulasContainer .formula-card .formula-header,
.formulas-list .formula-card .formula-header {
    display: flex;
    flex-direction: column;
    gap: 6px;
    align-items: center;
    width: 100%;
}

#formulasContainer .formula-title,
.formulas-list .formula-card .formula-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-header);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    width: 100%;
}

#formulasContainer .formula-card .formula-description,
#formulasContainer .formula-card .formula-display,
.formulas-list .formula-card .formula-description,
.formulas-list .formula-card .formula-display {
    /* Compact grid: hide verbose fields to keep cards concise.
       They will still be available in the modal. If you prefer to show them,
       remove the display: none rule. */
    display: none;
}

#formulasContainer .formula-button,
.formulas-list .formula-card .formula-button {
    padding: 8px 12px;
    font-size: 0.9rem;
    border-radius: var(--radius-full);
    width: auto;
}

/* Recent calculations grid */
#recentCalculationsContainer,
.recent-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: var(--space-md);
    padding: var(--space-lg);
}

#recentCalculationsContainer .recent-calculation-item,
.recent-list .recent-calculation-item {
    padding: var(--space-md);
    min-height: 90px;
    text-align: center;
    border-radius: var(--radius-md);
    background: linear-gradient(145deg, var(--bg-medium) 0%, var(--bg-light) 100%);
    border: 1px solid var(--bg-lighter);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
}

/* Small devices: force single column and slightly reduced padding */
@media (max-width: 420px) {
    #categoriesContainer,
    #subcategoriesContainer,
    #formulasContainer,
    #recentCalculationsContainer {
        grid-template-columns: 1fr;
        padding: var(--space-md);
    }

    #categoriesContainer .category-item,
    #subcategoriesContainer .subcategory-item,
    #formulasContainer .formula-card,
    #recentCalculationsContainer .recent-calculation-item {
        min-height: initial;
        padding: var(--space-sm);
    }
}

/* Accessibility: ensure focus states remain visible */
#categoriesContainer .category-item:focus,
#subcategoriesContainer .subcategory-item:focus,
#formulasContainer .formula-card:focus,
#recentCalculationsContainer .recent-calculation-item:focus {
    outline: 3px solid rgba(var(--primary-rgb), 0.15);
    outline-offset: 2px;
}