:root {
    --primary: #28a745;
    --primary-dark: #218838;
    --primary-light: #34ce57;
    --success: #28a745;
    --danger: #dc3545;
    --warning: #ffc107;
    --dark: #1f2937;
    --light: #f9fafb;
    --gray: #6b7280;
    --gray-light: #e5e7eb;
    --border: 6px;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #f0f9ff 0%, #e6f7ff 100%);
    color: var(--dark);
    line-height: 1.6;
    min-height: 100vh;
}

/* Header */
.header {
    background: white;
    border-bottom: 1px solid var(--gray-light);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 1px 10px rgba(0, 0, 0, 0.05);
}

.header-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    font-size: 22px;
    font-weight: 700;
    color: var(--primary);
    gap: 12px;
}

.logo-icon {
    width: 36px;
    height: 36px;
    background: var(--primary);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
}

.nav {
    display: flex;
    gap: 32px;
    align-items: center;
}

.nav-link {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    font-size: 15px;
    padding: 8px 0;
    position: relative;
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary);
}

.nav-link.active {
    color: var(--primary);
    font-weight: 600;
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--primary);
    border-radius: 2px;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.user-btn {
    background: var(--light);
    border: 1px solid var(--gray-light);
    border-radius: var(--border);
    padding: 8px 16px;
    font-size: 14px;
    font-weight: 500;
    color: var(--dark);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: var(--transition);
}

.user-btn:hover {
    background: var(--gray-light);
    border-color: var(--gray);
}

/* Main Content */
.main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 24px;
}

/* Hero Section */
.hero {
    text-align: center;
    margin-bottom: 48px;
    padding: 0 20px;
}

.hero-title {
    font-size: 42px;
    font-weight: 800;
    color: var(--dark);
    margin-bottom: 16px;
    line-height: 1.2;
}

.hero-title span {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 18px;
    color: var(--gray);
    max-width: 600px;
    margin: 0 auto 32px;
}

/* Card Container */
.card {
    background: white;
    border-radius: 16px;
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: var(--transition);
}

.card:hover {
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.12);
    transform: translateY(-4px);
}

.card-header {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    padding: 24px 32px;
    color: white;
}

.card-title {
    font-size: 20px;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 0;
}

.card-body {
    padding: 32px;
}

/* Form Grid */
.form-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
    margin-bottom: 32px;
}

@media (max-width: 768px) {
    .form-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
}

.form-group {
    margin-bottom: 0;
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 600;
    color: var(--dark);
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.form-label span {
    color: var(--danger);
}

.form-note {
    font-size: 12px;
    color: var(--danger);
    margin-top: 4px;
    font-style: italic;
    display: block;
}

.form-control {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid var(--gray-light);
    border-radius: var(--border);
    font-size: 15px;
    font-family: inherit;
    background: white;
    color: var(--dark);
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(40, 167, 69, 0.1);
}

.form-control::placeholder {
    color: #9ca3af;
}

select.form-control {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%236b7280'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M19 9l-7 7-7-7'%3E%3C/path%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 16px center;
    background-size: 20px;
    padding-right: 48px;
    cursor: pointer;
}

/* Calculation Box */
.calculation-box {
    background: linear-gradient(135deg, #28a745 0%, #20c997 100%);
    border-radius: 12px;
    padding: 28px;
    margin: 32px 0;
    color: white;
    position: relative;
    overflow: hidden;
}

.calculation-box::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    animation: shimmer 2s infinite;
}

@keyframes shimmer {
    0% { transform: translateX(-100%); }
    100% { transform: translateX(100%); }
}

.calculation-label {
    font-size: 14px;
    opacity: 0.9;
    margin-bottom: 8px;
    font-weight: 500;
}

.calculation-value {
    font-size: 36px;
    font-weight: 800;
    margin: 8px 0;
    text-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.calculation-note {
    font-size: 13px;
    opacity: 0.8;
    margin-top: 12px;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 16px 32px;
    font-size: 16px;
    font-weight: 600;
    border: none;
    border-radius: var(--border);
    cursor: pointer;
    text-decoration: none;
    transition: var(--transition);
    font-family: inherit;
    gap: 12px;
    min-height: 56px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    width: 100%;
    font-size: 17px;
    letter-spacing: 0.5px;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(40, 167, 69, 0.3);
}

.btn-primary:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.btn-icon {
    font-size: 18px;
}

/* Notification */
.notification {
    position: fixed;
    top: 90px;
    right: 24px;
    padding: 16px 20px;
    border-radius: var(--border);
    background: white;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
    display: flex;
    align-items: center;
    gap: 12px;
    z-index: 9999;
    animation: slideIn 0.3s ease;
    max-width: 400px;
    border-left: 4px solid var(--success);
}

.notification.error {
    border-left-color: var(--danger);
}

.notification.warning {
    border-left-color: var(--warning);
}

.notification-icon {
    font-size: 20px;
}

.notification.success .notification-icon {
    color: var(--success);
}

.notification.error .notification-icon {
    color: var(--danger);
}

.notification.warning .notification-icon {
    color: var(--warning);
}

.notification-content {
    flex: 1;
}

.notification-title {
    font-weight: 600;
    margin-bottom: 4px;
}

.notification-message {
    font-size: 14px;
    color: var(--gray);
}

.notification-close {
    background: none;
    border: none;
    color: var(--gray);
    cursor: pointer;
    padding: 4px;
    font-size: 18px;
    opacity: 0.7;
    transition: var(--transition);
}

.notification-close:hover {
    opacity: 1;
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

/* Loading Overlay */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(4px);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 10000;
}

.loading-content {
    text-align: center;
    color: white;
}

.loading-spinner {
    width: 60px;
    height: 60px;
    border: 3px solid rgba(255, 255, 255, 0.1);
    border-top: 3px solid white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

.loading-text {
    font-size: 16px;
    font-weight: 500;
    letter-spacing: 1px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Info Section */
.info-section {
    margin-top: 48px;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
}

.info-card {
    background: white;
    border-radius: 12px;
    padding: 24px;
    border: 1px solid var(--gray-light);
}

.info-card-title {
    font-size: 16px;
    font-weight: 700;
    color: var(--dark);
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.info-list {
    list-style: none;
}

.info-list li {
    padding: 10px 0;
    border-bottom: 1px solid var(--gray-light);
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 14px;
    color: var(--gray);
}

.info-list li:last-child {
    border-bottom: none;
}

.info-list i {
    color: var(--success);
    font-size: 12px;
}

/* Error States */
.error {
    border-color: var(--danger) !important;
}

.error-text {
    color: var(--danger);
    font-size: 13px;
    margin-top: 6px;
    display: none;
    align-items: center;
    gap: 6px;
}

.has-error .error-text {
    display: flex;
}

/* Footer */
.footer {
    background: var(--dark);
    color: white;
    padding: 60px 24px;
    margin-top: 80px;
}

.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
}

.footer-section h3 {
    font-size: 18px;
    margin-bottom: 20px;
    font-weight: 600;
}

.footer-section p {
    color: #9ca3af;
    font-size: 14px;
    line-height: 1.6;
}

.footer-bottom {
    text-align: center;
    padding-top: 40px;
    margin-top: 40px;
    border-top: 1px solid #374151;
    color: #9ca3af;
    font-size: 14px;
}

/* Responsive */
@media (max-width: 768px) {
    .header-container {
        padding: 0 16px;
        height: 60px;
    }

    .nav {
        display: none;
    }

    .hero-title {
        font-size: 32px;
    }

    .hero-subtitle {
        font-size: 16px;
    }

    .card-header {
        padding: 20px;
    }

    .card-body {
        padding: 24px;
    }

    .calculation-value {
        font-size: 28px;
    }

    .btn {
        padding: 14px 24px;
    }

    .main {
        padding: 24px 16px;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 28px;
    }

    .card-title {
        font-size: 18px;
    }

    .form-control {
        padding: 12px;
    }
}

/* Utility Classes */
.text-center {
    text-align: center;
}

.mt-4 {
    margin-top: 24px;
}

.mb-4 {
    margin-bottom: 24px;
}

.mb-6 {
    margin-bottom: 32px;
}

.hidden {
    display: none !important;
}

.w-full {
    width: 100%;
}

/* Mobile Menu Toggle */
.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    color: var(--dark);
    cursor: pointer;
    padding: 8px;
}

@media (max-width: 768px) {
    .menu-toggle {
        display: block;
    }
    
    .nav.mobile-open {
        display: flex;
        position: fixed;
        top: 60px;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 20px;
        box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
        z-index: 999;
    }
}

/* Close mobile menu when clicking outside */
@media (max-width: 768px) {
    .nav.mobile-open + .main-overlay {
        display: block;
    }
}