:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    --dark-bg: #1f2937;
    --dark-card: #374151;
    --dark-text: #f9fafb;
    --light-bg: #f9fafb;
    --light-card: #ffffff;
    --light-text: #1f2937;
    --border-radius: 8px;
    --box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, var(--light-bg) 0%, #e0f2fe 100%);
    color: var(--light-text);
    transition: var(--transition);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

body.dark-mode {
    background: linear-gradient(135deg, var(--dark-bg) 0%, #1e3a8a 100%);
    color: var(--dark-text);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
    flex: 1;
}

/* Header Styles */
header {
    background-color: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: var(--transition);
}

.dark-mode header {
    background-color: rgba(31, 41, 55, 0.9);
}

.header-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-container {
    display: flex;
    align-items: center;
}

.logo-container a {
    display: flex;
    align-items: center;
    text-decoration: none;
}

.logo {
    height: 40px;
    margin-right: 15px;
}

.site-title {
    font-size: 24px;
    font-weight: 600;
    background: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.nav-actions {
    display: flex;
    gap: 15px;
}

#theme-btn {
    background: none;
    border: none;
    font-size: 18px;
    cursor: pointer;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    color: var(--light-text);
    background-color: #e2e8f0;
}

.dark-mode #theme-btn {
    color: var(--dark-text);
    background-color: #4b5563;
}

#theme-btn:hover {
    background-color: var(--primary-color);
    color: white;
    transform: rotate(30deg);
}

/* Page Title */
.page-title {
    text-align: center;
    margin: 30px 0;
}

.page-title h1 {
    font-size: 36px;
    margin-bottom: 10px;
    background: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.page-title p {
    font-size: 18px;
    color: #64748b;
}

.dark-mode .page-title p {
    color: #9ca3af;
}

/* Calculator Styles */
.calculator-container {
    display: flex;
    flex-wrap: wrap;
    gap: 30px;
    justify-content: center;
    margin: 40px auto;
    max-width: 1000px;
}

.calculator {
    background-color: var(--light-card);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 20px;
    width: 100%;
    max-width: 500px;
    transition: var(--transition);
}

.dark-mode .calculator {
    background-color: var(--dark-card);
}

.display-container {
    background-color: #f8fafc;
    border-radius: var(--border-radius);
    margin-bottom: 20px;
    padding: 15px;
    text-align: right;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
}

.dark-mode .display-container {
    background-color: #1e293b;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.2);
}

.history {
    color: #64748b;
    font-size: 14px;
    min-height: 20px;
    margin-bottom: 8px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.dark-mode .history {
    color: #9ca3af;
}

.display {
    font-size: 40px;
    font-weight: 600;
    overflow: hidden;
    text-overflow: ellipsis;
    min-height: 50px;
}

.dark-mode .display {
    color: #f9fafb;
}

.button-container {
    display: grid;
    gap: 10px;
}

.button-row {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}

.btn {
    background-color: #f1f5f9;
    border: none;
    border-radius: var(--border-radius);
    color: var(--light-text);
    cursor: pointer;
    font-size: 18px;
    font-weight: 500;
    padding: 15px 10px;
    transition: var(--transition);
    user-select: none;
}

.dark-mode .btn {
    background-color: #334155;
    color: var(--dark-text);
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.btn:active {
    transform: translateY(0);
    box-shadow: none;
}

.function {
    background-color: #e2e8f0;
}

.dark-mode .function {
    background-color: #475569;
}

.number {
    background-color: #f8fafc;
}

.dark-mode .number {
    background-color: #1e293b;
}

.operator {
    background-color: #dbeafe;
    color: var(--primary-color);
    font-weight: 600;
}

.dark-mode .operator {
    background-color: #1e3a8a;
    color: #93c5fd;
}

.equals {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    font-weight: 600;
}

.memory {
    background-color: #ede9fe;
    color: var(--secondary-color);
    font-size: 14px;
}

.dark-mode .memory {
    background-color: #4c1d95;
    color: #ddd6fe;
}

.calculator-info {
    background-color: var(--light-card);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 20px;
    width: 100%;
    max-width: 400px;
}

.dark-mode .calculator-info {
    background-color: var(--dark-card);
}

.calculator-info h3 {
    color: var(--primary-color);
    margin-bottom: 10px;
    font-size: 18px;
}

.dark-mode .calculator-info h3 {
    color: #93c5fd;
}

.calculator-info ul {
    list-style-type: none;
    margin-bottom: 20px;
}

.calculator-info li {
    margin-bottom: 5px;
    font-size: 14px;
    color: #64748b;
}

.dark-mode .calculator-info li {
    color: #9ca3af;
}

.calculator-info strong {
    color: var(--light-text);
    font-weight: 600;
}

.dark-mode .calculator-info strong {
    color: var(--dark-text);
}

/* Footer styles */
.footer {
    margin-top: 40px;
    padding: 20px 0;
    text-align: center;
    border-top: 1px solid #e2e8f0;
    background-color: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(10px);
    transition: var(--transition);
}

.dark-mode .footer {
    background-color: rgba(31, 41, 55, 0.8);
    border-top-color: #4b5563;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.footer p {
    margin: 10px 0;
    font-size: 14px;
    color: #64748b;
}

.dark-mode .footer p {
    color: #9ca3af;
}

.footer-links {
    line-height: 1.6;
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

.footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Responsive styles */
@media (max-width: 768px) {
    .calculator-container {
        flex-direction: column;
        align-items: center;
    }
    
    .button-row {
        gap: 8px;
    }
    
    .btn {
        font-size: 16px;
        padding: 12px 8px;
    }
    
    .display {
        font-size: 32px;
    }
}

@media (max-width: 480px) {
    .button-row {
        gap: 5px;
    }
    
    .btn {
        font-size: 14px;
        padding: 10px 5px;
    }
    
    .memory {
        font-size: 12px;
    }
    
    .display {
        font-size: 28px;
    }
}