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

:root {
    --primary-color: #2563eb;
    --secondary-color: #10b981;
    --accent-color: #f59e0b;
    --danger-color: #ef4444;
    --dark-color: #1f2937;
    --light-color: #f3f4f6;
    --border-color: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark-color);
    background-color: #ffffff;
}

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

/* Navigation */
.navbar {
    background: white;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

.logo i {
    margin-right: 0.5rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-menu a {
    text-decoration: none;
    color: var(--dark-color);
    font-weight: 500;
    transition: color 0.3s;
}

.nav-menu a:hover,
.nav-menu a.active {
    color: var(--primary-color);
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--dark-color);
    margin: 3px 0;
    transition: 0.3s;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 80px 0;
    text-align: center;
}

.hero-content h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 12px 24px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: white;
    color: var(--primary-color);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: transparent;
    color: white;
    border: 2px solid white;
}

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

.btn-outline {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-outline:hover {
    background: var(--primary-color);
    color: white;
}

/* Tools Section */
.tools-section {
    padding: 80px 0;
    background: var(--light-color);
}

.tools-section h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--dark-color);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.tool-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.3s, box-shadow 0.3s;
}

.tool-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.tool-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 1rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 2rem;
}

.tool-card h3 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
    color: var(--dark-color);
}

.tool-card p {
    color: #6b7280;
    margin-bottom: 1.5rem;
}

/* Features Section */
.features-section {
    padding: 80px 0;
}

.features-section h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--dark-color);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.feature {
    text-align: center;
    padding: 2rem;
}

.feature i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.feature h3 {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: var(--dark-color);
}

.feature p {
    color: #6b7280;
}

/* Footer */
footer {
    background: var(--dark-color);
    color: white;
    text-align: center;
    padding: 2rem 0;
}

/* Calculator Pages */
.calculator-section {
    padding: 40px 0;
    min-height: calc(100vh - 200px);
}

.calculator-container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
}

.calculator-header {
    text-align: center;
    margin-bottom: 2rem;
}

.calculator-header h1 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.calculator-header p {
    color: #6b7280;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--dark-color);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.btn-calculate {
    width: 100%;
    background: var(--primary-color);
    color: white;
    padding: 14px;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s;
}

.btn-calculate:hover {
    background: #1d4ed8;
}

.results {
    margin-top: 2rem;
    padding: 2rem;
    background: var(--light-color);
    border-radius: 8px;
    display: none;
}

.results.show {
    display: block;
}

.result-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
}

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

.result-label {
    font-weight: 600;
    color: var(--dark-color);
}

.result-value {
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--primary-color);
}

/* Expense Tracker Styles */
.expense-form {
    background: var(--light-color);
    padding: 2rem;
    border-radius: 8px;
    margin-bottom: 2rem;
}

.expense-list {
    max-height: 400px;
    overflow-y: auto;
}

.expense-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: white;
    border-radius: 8px;
    margin-bottom: 0.5rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.expense-info {
    flex: 1;
}

.expense-amount {
    font-weight: bold;
    color: var(--primary-color);
}

.expense-category {
    display: inline-block;
    padding: 0.25rem 0.5rem;
    background: var(--secondary-color);
    color: white;
    border-radius: 4px;
    font-size: 0.8rem;
    margin-left: 0.5rem;
}

.btn-delete {
    background: var(--danger-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    cursor: pointer;
    transition: background 0.3s;
}

.btn-delete:hover {
    background: #dc2626;
}

.summary-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.summary-card {
    background: white;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
    text-align: center;
}

.summary-card h3 {
    color: #6b7280;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.summary-card .amount {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background-color: white;
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow);
        padding: 2rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .hamburger {
        display: flex;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .hero-content p {
        font-size: 1rem;
    }

    .tools-grid {
        grid-template-columns: 1fr;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

    .summary-cards {
        grid-template-columns: 1fr;
    }
}

/* Loading Animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Toast Notification */
.toast {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background: var(--dark-color);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: 8px;
    box-shadow: var(--shadow-lg);
    transform: translateX(400px);
    transition: transform 0.3s;
    z-index: 1000;
}

.toast.show {
    transform: translateX(0);
}

.toast.success {
    background: var(--secondary-color);
}

.toast.error {
    background: var(--danger-color);
}