/* CSS Variables for Dark Theme */
:root {
    /* Dark Theme Colors */
    --bg-primary: #0f0f23;
    --bg-secondary: rgba(30, 30, 50, 0.8);
    --bg-tertiary: rgba(30, 30, 50, 0.6);
    --text-primary: #ffffff;
    --text-secondary: #a0a0a0;
    --accent-primary: #818cf8;
    --accent-secondary: #a78bfa;
    --accent-danger: #f87171;
    --accent-success: #34d399;
    --accent-warning: #fbbf24;
    --border-color: rgba(255, 255, 255, 0.1);
    --shadow-light: rgba(0, 0, 0, 0.3);
    --shadow-dark: rgba(0, 0, 0, 0.5);
    --glass-bg: rgba(30, 30, 50, 0.25);
    --glass-border: rgba(255, 255, 255, 0.1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    transition: all 0.3s ease;
    overflow-x: hidden;
}

/* Calculator Container */
.calculator-container {
    position: relative;
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}



/* Calculator Body */
.calculator {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    box-shadow: 
        0 8px 32px var(--shadow-light),
        inset 0 1px 0 rgba(255, 255, 255, 0.1);
    overflow: hidden;
    transition: all 0.3s ease;
    display: flex;
    flex-direction: row;
    width: 100%;
    max-width: 1000px;
}

.calculator:hover {
    transform: translateY(-2px);
    box-shadow: 
        0 12px 40px var(--shadow-dark),
        inset 0 1px 0 rgba(255, 255, 255, 0.1);
}

/* Display Section */
.display-section {
    position: relative;
    padding: 30px 25px 20px;
    background: linear-gradient(135deg, var(--bg-tertiary) 0%, var(--bg-secondary) 100%);
    border-right: 1px solid var(--border-color);
    min-width: 300px;
    flex-shrink: 0;
}

.memory-indicator {
    position: absolute;
    top: 15px;
    left: 25px;
    width: 24px;
    height: 24px;
    background: var(--accent-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: 600;
    opacity: 0;
    transform: scale(0);
    transition: all 0.3s ease;
}

.memory-indicator.active {
    opacity: 1;
    transform: scale(1);
}

.display {
    text-align: right;
    min-height: 80px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

.expression {
    font-size: 18px;
    color: var(--text-secondary);
    margin-bottom: 8px;
    min-height: 27px;
    word-wrap: break-word;
    transition: all 0.3s ease;
}

.result {
    font-size: 36px;
    font-weight: 600;
    color: var(--text-primary);
    line-height: 1.2;
    word-wrap: break-word;
    transition: all 0.3s ease;
}

/* Buttons Grid */
.buttons-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: var(--border-color);
    padding: 1px;
    flex: 1;
    min-width: 400px;
}

/* Button Base Styles */
.btn {
    border: none;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    color: var(--text-primary);
    font-family: inherit;
    font-size: 18px;
    font-weight: 500;
    padding: 20px 10px;
    cursor: pointer;
    transition: all 0.2s ease;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 60px;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    transition: width 0.3s ease, height 0.3s ease;
}

.btn:active::before {
    width: 100px;
    height: 100px;
}

.btn:hover {
    background: var(--bg-secondary);
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(0);
}

/* Button Types */
.number-btn {
    background: var(--glass-bg);
    font-weight: 600;
}

.number-btn:hover {
    background: var(--bg-secondary);
}

.operator-btn {
    background: rgba(99, 102, 241, 0.1);
    color: var(--accent-primary);
    font-weight: 600;
}

.operator-btn:hover {
    background: rgba(99, 102, 241, 0.2);
}

.function-btn {
    background: rgba(139, 92, 246, 0.1);
    color: var(--accent-secondary);
    font-size: 16px;
    font-weight: 500;
}

.function-btn:hover {
    background: rgba(139, 92, 246, 0.2);
}

.clear-btn {
    background: rgba(239, 68, 68, 0.1);
    color: var(--accent-danger);
    font-weight: 600;
}

.clear-btn:hover {
    background: rgba(239, 68, 68, 0.2);
}

.equals-btn {
    background: linear-gradient(135deg, var(--accent-success) 0%, var(--accent-primary) 100%);
    color: white;
    font-weight: 600;
    font-size: 20px;
}

.equals-btn:hover {
    background: linear-gradient(135deg, var(--accent-success) 20%, var(--accent-primary) 100%);
    transform: translateY(-2px);
}

.memory-btn {
    background: rgba(16, 185, 129, 0.1);
    color: var(--accent-success);
    font-size: 14px;
    font-weight: 600;
}

.memory-btn:hover {
    background: rgba(16, 185, 129, 0.2);
}

/* Footer */
.footer {
    width: 100%;
    max-width: 1000px;
    margin-top: 20px;
    padding: 20px;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    text-align: center;
    transition: all 0.3s ease;
}

.footer-content {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.footer-content p {
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    margin: 0;
}

.footer-content p:first-child {
    color: var(--text-primary);
    font-weight: 600;
    font-size: 16px;
}

/* Keyboard Info */
.keyboard-info {
    margin-top: 20px;
    text-align: center;
    color: var(--text-secondary);
    font-size: 14px;
}

.keyboard-info p {
    margin-bottom: 10px;
    font-weight: 500;
}

.keyboard-shortcuts {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    justify-content: center;
}

.keyboard-shortcuts span {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    padding: 8px 12px;
    border-radius: 8px;
    font-size: 12px;
    font-weight: 500;
}

/* Responsive Design */
@media (max-width: 768px) {
    body {
        padding: 10px;
    }
    
    .calculator-container {
        max-width: 100%;
    }
    

    
    .calculator {
        flex-direction: column;
        max-width: 400px;
    }
    
    .display-section {
        border-right: none;
        border-bottom: 1px solid var(--border-color);
        min-width: auto;
    }
    
    .buttons-grid {
        min-width: auto;
    }
    
    .btn {
        padding: 15px 8px;
        font-size: 16px;
        min-height: 50px;
    }
    
    .result {
        font-size: 28px;
    }
    
    .expression {
        font-size: 16px;
    }
    
    .keyboard-shortcuts {
        flex-direction: column;
        align-items: center;
    }
    
    .footer {
        max-width: 400px;
    }
}

@media (max-width: 480px) {
    .btn {
        padding: 12px 6px;
        font-size: 14px;
        min-height: 45px;
    }
    
    .result {
        font-size: 24px;
    }
    
    .expression {
        font-size: 14px;
    }
}

@media (max-width: 360px) {
    .btn {
        padding: 12px 6px;
        font-size: 14px;
        min-height: 45px;
    }
    
    .result {
        font-size: 24px;
    }
    
    .expression {
        font-size: 14px;
    }
}

/* Animation Classes */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

@keyframes ripple {
    0% {
        transform: scale(0);
        opacity: 1;
    }
    100% {
        transform: scale(4);
        opacity: 0;
    }
}

.calculator {
    animation: fadeIn 0.6s ease-out;
}

.btn:active {
    animation: pulse 0.2s ease;
}

/* Error State */
.error {
    color: var(--accent-danger) !important;
    animation: pulse 0.3s ease;
}

/* Success State */
.success {
    color: var(--accent-success) !important;
    animation: pulse 0.3s ease;
}

/* Loading State */
.loading {
    opacity: 0.7;
    pointer-events: none;
}

/* Focus States for Accessibility */
.btn:focus {
    outline: 2px solid var(--accent-primary);
    outline-offset: 2px;
}

/* High Contrast Mode Support */
@media (prefers-contrast: high) {
    :root {
        --border-color: rgba(0, 0, 0, 0.3);
        --glass-bg: rgba(255, 255, 255, 0.9);
    }
    
    [data-theme="dark"] {
        --border-color: rgba(255, 255, 255, 0.3);
        --glass-bg: rgba(0, 0, 0, 0.9);
    }
}

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