:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --warning-color: #f59e0b;
    --error-color: #dc3545;
    --info-color: #17a2b8;
    --background-color: #f8f9fa;
    --surface-color: #ffffff;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --border-color: #dee2e6;
    --border-radius: 16px;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.15);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --gradient-primary: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
    --gradient-success: linear-gradient(135deg, #28a745 0%, #20c997 100%);
    --gradient-warning: linear-gradient(135deg, #f59e0b 0%, #fbbf24 100%);
    --gradient-error: linear-gradient(135deg, #dc3545 0%, #e83e8c 100%);
    --glass-effect: rgba(255, 255, 255, 0.1);
    --glass-border: rgba(255, 255, 255, 0.2);
}

[data-theme="dark"] {
    --primary-color: #3b82f6;
    --primary-dark: #2563eb;
    --secondary-color: #6b7280;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --error-color: #ef4444;
    --info-color: #06b6d4;
    --background-color: #0f172a;
    --surface-color: #1e293b;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: #334155;
    --gradient-primary: linear-gradient(135deg, #3b82f6 0%, #1d4ed8 100%);
    --gradient-success: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-warning: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
    --gradient-error: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    --glass-effect: rgba(30, 41, 59, 0.6);
    --glass-border: rgba(255, 255, 255, 0.1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-touch-callout: none;
    -webkit-tap-highlight-color: transparent;
}

html {
    overflow: hidden;
    height: 100%;
    -webkit-text-size-adjust: 100%;
    -ms-text-size-adjust: 100%;
    text-size-adjust: 100%;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--background-color);
    color: var(--text-primary);
    line-height: 1.5;
    transition: var(--transition);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    background-image: 
        radial-gradient(circle at 10% 20%, rgba(37, 99, 235, 0.08) 0%, transparent 25%),
        radial-gradient(circle at 90% 80%, rgba(59, 130, 246, 0.08) 0%, transparent 25%);
    backdrop-filter: blur(20px);
    overflow: hidden;
    touch-action: manipulation;
    height: 100%;
    position: fixed;
    width: 100%;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

[data-theme="dark"] body {
    background-image: 
        radial-gradient(circle at 10% 20%, rgba(59, 130, 246, 0.12) 0%, transparent 25%),
        radial-gradient(circle at 90% 80%, rgba(37, 99, 235, 0.12) 0%, transparent 25%);
}

.calculator-container {
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
    height: 100%;
    display: flex;
    align-items: center;
}

.calculator {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    border: 1px solid var(--border-color);
    position: relative;
    transition: var(--transition);
    backdrop-filter: blur(10px);
    background: var(--glass-effect);
    width: 100%;
    max-height: 90vh;
    display: flex;
    flex-direction: column;
}

.calculator::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
    z-index: 10;
}

.calculator-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
    background: var(--surface-color);
    position: relative;
    backdrop-filter: blur(10px);
    flex-shrink: 0;
}

.calculator-title h1 {
    font-size: clamp(18px, 4vw, 26px);
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 4px;
    display: flex;
    align-items: center;
    gap: 10px;
    letter-spacing: -0.5px;
}

.calculator-title h1 i {
    color: var(--primary-color);
    font-size: clamp(20px, 4vw, 28px);
}

.calculator-subtitle {
    font-size: clamp(12px, 2.5vw, 14px);
    color: var(--primary-color);
    font-weight: 500;
    letter-spacing: 0.5px;
    opacity: 0.9;
}

.header-actions {
    display: flex;
    gap: 10px;
    align-items: center;
}

.theme-toggle, .github-link {
    background: var(--background-color);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 10px;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-primary);
    font-size: 14px;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.theme-toggle:hover, 
.github-link:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px) scale(1.05);
    box-shadow: 0 6px 20px rgba(37, 99, 235, 0.3);
    background: var(--surface-color);
}

.theme-toggle i, 
.github-link i {
    color: var(--text-primary);
    transition: var(--transition);
    position: relative;
    z-index: 2;
}

.theme-toggle:hover i, 
.github-link:hover i {
    color: var(--text-primary);
    transform: scale(1.1);
}

[data-theme="dark"] .theme-toggle i,
[data-theme="dark"] .github-link i {
    color: white;
}

[data-theme="dark"] .theme-toggle:hover i,
[data-theme="dark"] .github-link:hover i {
    color: white;
}

.display-container {
    padding: 20px 24px;
    background: var(--background-color);
    border-bottom: 1px solid var(--border-color);
    position: relative;
    backdrop-filter: blur(10px);
    flex-shrink: 0;
}

.expression-display {
    font-size: clamp(13px, 3vw, 15px);
    color: var(--text-secondary);
    min-height: 20px;
    margin-bottom: 8px;
    text-align: right;
    font-weight: 400;
    font-family: 'Courier New', monospace;
    letter-spacing: 0.5px;
    word-break: break-all;
    overflow-wrap: break-word;
}

.main-display {
    text-align: right;
    margin-bottom: 8px;
    min-height: 50px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
}

.display-value {
    font-size: clamp(24px, 6vw, 38px);
    font-weight: 700;
    color: var(--text-primary);
    word-break: break-all;
    font-family: 'Courier New', monospace;
    letter-spacing: 1px;
    line-height: 1.2;
    overflow-wrap: break-word;
}

.display-format {
    position: absolute;
    top: 12px;
    left: 16px;
    font-size: 11px;
    color: var(--text-secondary);
    background: var(--surface-color);
    padding: 4px 8px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    font-weight: 500;
}

.status-bar {
    display: flex;
    justify-content: space-between;
    padding: 12px 20px;
    background: var(--background-color);
    border-bottom: 1px solid var(--border-color);
    font-size: clamp(11px, 2.5vw, 13px);
    flex-wrap: wrap;
    gap: 12px;
    backdrop-filter: blur(10px);
    flex-shrink: 0;
}

.status-item {
    display: flex;
    align-items: center;
    gap: 5px;
}

.status-label {
    color: var(--text-secondary);
    font-weight: 500;
}

.status-value {
    color: var(--text-primary);
    font-weight: 600;
    background: var(--surface-color);
    padding: 3px 8px;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    min-width: 40px;
    text-align: center;
    font-size: 11px;
}

.tabs-container {
    padding: 12px 20px 0;
    border-bottom: 1px solid var(--border-color);
    backdrop-filter: blur(10px);
    transform: translateY(-1px);
    position: relative;
    z-index: 5;
    flex-shrink: 0;
}

.tabs {
    display: flex;
    gap: 3px;
    background: var(--background-color);
    border-radius: 10px;
    padding: 5px;
    border: 1px solid var(--border-color);
}

.tab {
    flex: 1;
    padding: 10px 12px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-weight: 600;
    cursor: pointer;
    border-radius: 6px;
    transition: var(--transition);
    font-size: clamp(11px, 2.5vw, 13px);
    text-align: center;
    letter-spacing: 0.3px;
    white-space: nowrap;
}

.tab.active {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
    transform: translateY(-1px);
}

.tab:hover:not(.active) {
    background: var(--surface-color);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.buttons-grid {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 8px;
    padding: 20px;
    transition: var(--transition);
    flex: 1;
    overflow-y: auto;
    min-height: 0;
}

.buttons-grid.hidden {
    display: none;
}

.secondary-panel {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
    padding: 0 20px 20px;
    justify-content: center;
    flex-shrink: 0;
}

.history-panel {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--surface-color);
    z-index: 100;
    padding: 20px;
    display: flex;
    flex-direction: column;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
}

.history-panel.hidden {
    display: none;
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
}

.history-header h3 {
    color: var(--text-primary);
    font-weight: 700;
    font-size: clamp(16px, 4vw, 20px);
}

.history-list {
    flex: 1;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 12px;
    min-height: 0;
}

.history-item {
    padding: 14px;
    background: var(--background-color);
    border-radius: 10px;
    border: 1px solid var(--border-color);
    cursor: pointer;
    transition: var(--transition);
    backdrop-filter: blur(10px);
    flex-shrink: 0;
}

.history-item:hover {
    background: var(--surface-color);
    border-color: var(--primary-color);
    transform: translateX(6px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.history-expression {
    font-size: clamp(12px, 2.5vw, 14px);
    color: var(--text-secondary);
    margin-bottom: 5px;
    font-family: 'Courier New', monospace;
    word-break: break-all;
}

.history-result {
    font-size: clamp(14px, 3vw, 17px);
    color: var(--text-primary);
    font-weight: 700;
    font-family: 'Courier New', monospace;
    word-break: break-all;
}

.btn {
    border: 1px solid var(--border-color);
    border-radius: 10px;
    padding: 10px 6px;
    font-family: inherit;
    font-size: clamp(12px, 2.5vw, 14px);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    background: var(--surface-color);
    color: var(--text-primary);
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(10px);
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    text-align: center;
    white-space: nowrap;
    touch-action: manipulation;
}

.btn:hover {
    transform: translateY(-2px) scale(1.02);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.12);
    border-color: var(--primary-color);
    background: var(--surface-color);
}

.btn:active {
    transform: scale(0.98);
}

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

.btn-number {
    background: var(--surface-color);
    color: var(--text-primary);
    font-weight: 700;
}

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

.btn-operator {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    font-weight: 700;
}

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

.btn-equals {
    background: var(--success-color);
    color: white;
    border-color: var(--success-color);
    font-weight: 700;
}

.btn-equals:hover {
    background: #218838;
    border-color: #218838;
}

.btn-function {
    background: #8B5CF6;
    color: white;
    border-color: #8B5CF6;
    font-weight: 600;
}

.btn-function:hover {
    background: #7C3AED;
    border-color: #7C3AED;
}

.btn-scientific {
    background: var(--background-color);
    color: var(--text-primary);
    border-color: var(--border-color);
    font-size: clamp(11px, 2.5vw, 13px);
    font-weight: 600;
}

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

.btn-memory {
    background: linear-gradient(135deg, #fef3c7 0%, #fde68a 100%);
    color: #92400e;
    border-color: #fcd34d;
    font-size: clamp(11px, 2.5vw, 12px);
    font-weight: 600;
}

[data-theme="dark"] .btn-memory {
    background: linear-gradient(135deg, #78350f 0%, #92400e 100%);
    color: #fef3c7;
    border-color: #d97706;
}

.btn-memory:hover {
    background: linear-gradient(135deg, #fde68a 0%, #fcd34d 100%);
    border-color: #fbbf24;
}

[data-theme="dark"] .btn-memory:hover {
    background: linear-gradient(135deg, #92400e 0%, #b45309 100%);
    border-color: #f59e0b;
}

.btn-secondary {
    background: var(--background-color);
    color: var(--text-primary);
    border-color: var(--border-color);
    font-size: clamp(11px, 2.5vw, 13px);
    font-weight: 600;
}

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

.btn-zero {
    grid-column: span 2;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .buttons-grid {
        grid-template-columns: repeat(4, 1fr);
    }
    
    .secondary-panel {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .calculator-container {
        max-width: 600px;
    }
}

@media (max-width: 768px) {
    body {
        padding: 10px;
    }
    
    .calculator-container {
        padding: 5px;
        max-height: 95vh;
    }
    
    .buttons-grid {
        grid-template-columns: repeat(4, 1fr);
        gap: 6px;
        padding: 15px;
    }
    
    .secondary-panel {
        grid-template-columns: repeat(2, 1fr);
        padding: 0 15px 15px;
    }
    
    .display-value {
        font-size: clamp(20px, 8vw, 28px);
    }
    
    .calculator-header {
        padding: 15px;
    }
    
    .calculator-title h1 {
        font-size: clamp(16px, 5vw, 20px);
    }
    
    .btn {
        padding: 8px 4px;
        font-size: clamp(11px, 3vw, 13px);
        min-height: 40px;
    }
    
    .status-bar {
        padding: 10px 15px;
        gap: 10px;
    }
    
    .tabs-container {
        padding: 10px 15px 0;
    }
    
    .display-container {
        padding: 15px;
    }
}

@media (max-width: 480px) {
    body {
        padding: 5px;
    }
    
    .calculator-container {
        padding: 2px;
    }
    
    .buttons-grid {
        grid-template-columns: repeat(4, 1fr);
        gap: 4px;
        padding: 10px;
    }
    
    .secondary-panel {
        grid-template-columns: repeat(2, 1fr);
        gap: 6px;
        padding: 0 10px 10px;
    }
    
    .display-value {
        font-size: clamp(18px, 9vw, 24px);
    }
    
    .btn {
        padding: 6px 3px;
        font-size: clamp(10px, 3.5vw, 12px);
        min-height: 36px;
    }
    
    .status-bar {
        flex-direction: column;
        gap: 8px;
        align-items: flex-start;
    }
    
    .status-item {
        width: 100%;
        justify-content: space-between;
    }
    
    .calculator-header {
        flex-direction: column;
        gap: 12px;
        text-align: center;
        padding: 12px;
    }
    
    .header-actions {
        justify-content: center;
    }
    
    .tabs {
        flex-wrap: wrap;
    }
    
    .tab {
        flex: 1 0 45%;
        margin: 2px;
    }
}

@media (max-width: 320px) {
    .buttons-grid {
        grid-template-columns: repeat(4, 1fr);
        gap: 3px;
        padding: 8px;
    }
    
    .btn {
        min-height: 32px;
        font-size: 10px;
        padding: 4px 2px;
    }
    
    .secondary-panel {
        grid-template-columns: repeat(2, 1fr);
        gap: 4px;
        padding: 0 8px 8px;
    }
}

/* Orientation-specific styles */
@media (max-height: 600px) and (orientation: landscape) {
    .calculator-container {
        max-height: 98vh;
    }
    
    .buttons-grid {
        grid-template-columns: repeat(8, 1fr);
        gap: 4px;
        padding: 8px;
    }
    
    .btn {
        min-height: 30px;
        font-size: 10px;
        padding: 4px 2px;
    }
    
    .calculator-header {
        padding: 8px 12px;
    }
    
    .display-container {
        padding: 8px 12px;
    }
    
    .status-bar {
        padding: 6px 12px;
    }
    
    .tabs-container {
        padding: 6px 12px 0;
    }
}

@keyframes buttonPress {
    0% { transform: scale(1); }
    50% { transform: scale(0.95); }
    100% { transform: scale(1); }
}

.btn.pressed {
    animation: buttonPress 0.15s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.calculator {
    animation: fadeIn 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.buttons-grid {
    animation: slideIn 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.history-list::-webkit-scrollbar {
    width: 6px;
}

.history-list::-webkit-scrollbar-track {
    background: var(--background-color);
    border-radius: 3px;
}

.history-list::-webkit-scrollbar-thumb {
    background: var(--primary-color);
    border-radius: 3px;
}

.history-list::-webkit-scrollbar-thumb:hover {
    background: var(--primary-dark);
}

.github-link {
    text-decoration: none !important;
}

.github-link i {
    text-decoration: none !important;
}

.hidden {
    display: none !important;
}

/* Safe area insets for modern mobile devices */
@supports(padding: max(0px)) {
    .calculator-container {
        padding-left: max(20px, env(safe-area-inset-left));
        padding-right: max(20px, env(safe-area-inset-right));
        padding-bottom: max(20px, env(safe-area-inset-bottom));
    }
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --border-color: #000000;
        --shadow: 0 4px 12px rgba(0, 0, 0, 0.5);
    }
    
    .btn {
        border-width: 2px;
    }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
    
    .btn:hover {
        transform: none;
    }
}