:root {
        --primary: #0052FF;
        --primary-dark: #003dcc;
        --secondary: #10B981;
        --danger: #EF4444;
        --dark: #0A0B0D;
        --gray: #6B7280;
        --light: #F5F7FA;
        --white: #FFFFFF;
        --radius: 8px;
        --shadow: 0 2px 8px rgba(0,0,0,0.1);
        --border: #E5E7EB;
    }
    
    .page-header {
        text-align: center;
        margin: 3rem 0;
    }
    
    .page-header h1 {
        font-size: 2.5rem;
        font-weight: 700;
        color: var(--dark);
        margin-bottom: 1rem;
    }
    
    .page-header p {
        font-size: 1.1rem;
        color: var(--gray);
        max-width: 600px;
        margin: 0 auto;
    }
    
    .messages-container {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 2rem;
        margin-bottom: 2rem;
    }
    
    .section-header {
        background: var(--light);
        padding: 1.5rem;
        border-bottom: 1px solid var(--border);
    }
    
    .section-header h2 {
        font-size: 1.5rem;
        font-weight: 600;
        color: var(--dark);
        margin: 0;
    }
    
    .form-card, .history-card {
        background: var(--white);
        border-radius: var(--radius);
        box-shadow: var(--shadow);
        overflow: hidden;
    }
    
    .form-card {
        padding: 1.5rem;
    }
    
    .message-form {
        max-width: 500px;
    }
    
    .form-group {
        margin-bottom: 1.5rem;
    }
    
    .form-group label {
        display: block;
        font-weight: 500;
        margin-bottom: 0.5rem;
        color: var(--dark);
    }
    
    .form-group input,
    .form-group textarea {
        width: 100%;
        padding: 0.75rem 1rem;
        border: 1px solid var(--border);
        border-radius: var(--radius);
        font-size: 1rem;
        transition: border-color 0.2s;
        font-family: inherit;
    }
    
    .form-group input:focus,
    .form-group textarea:focus {
        border-color: var(--primary);
        outline: none;
        box-shadow: 0 0 0 3px rgba(0, 82, 255, 0.1);
    }
    
    .form-group small {
        display: block;
        margin-top: 0.5rem;
        color: var(--gray);
        font-size: 0.8rem;
    }
    
    .btn-primary {
        background: var(--primary);
        color: var(--white);
        border: none;
        padding: 0.75rem 1.5rem;
        border-radius: var(--radius);
        font-size: 1rem;
        font-weight: 600;
        cursor: pointer;
        transition: background 0.2s;
        text-decoration: none;
        display: inline-block;
    }
    
    .btn-primary:hover {
        background: var(--primary-dark);
    }
    
    .alert {
        padding: 1rem;
        border-radius: var(--radius);
        margin-bottom: 1.5rem;
        display: flex;
        align-items: center;
        gap: 0.75rem;
    }
    
    .alert.success {
        background: #f0fdf4;
        color: #166534;
        border: 1px solid #bbf7d0;
    }
    
    .alert.error {
        background: #fef2f2;
        color: #b91c1c;
        border: 1px solid #fecaca;
    }
    
    .message-list {
        padding: 1.5rem;
        max-height: 500px;
        overflow-y: auto;
    }
    
    .message-item {
        background: var(--light);
        border-radius: var(--radius);
        padding: 1rem;
        margin-bottom: 1rem;
    }
    
    .message-item.sent {
        background: rgba(0, 82, 255, 0.05);
        border-left: 3px solid var(--primary);
    }
    
    .message-item.received {
        background: rgba(16, 185, 129, 0.05);
        border-left: 3px solid var(--secondary);
    }
    
    .message-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-bottom: 0.5rem;
    }
    
    .message-info {
        display: flex;
        flex-direction: column;
    }
    
    .message-subject {
        font-weight: 600;
        color: var(--dark);
    }
    
    .message-date {
        font-size: 0.8rem;
        color: var(--gray);
    }
    
    .message-direction {
        font-size: 0.8rem;
        padding: 0.25rem 0.5rem;
        border-radius: 9999px;
        background: var(--white);
    }
    
    .message-item.sent .message-direction {
        color: var(--primary);
    }
    
    .message-item.received .message-direction {
        color: var(--secondary);
    }
    
    .message-content {
        color: var(--dark);
        line-height: 1.5;
    }
    
    .empty-messages {
        text-align: center;
        padding: 3rem 1.5rem;
    }
    
    .empty-icon {
        font-size: 3rem;
        margin-bottom: 1rem;
    }
    
    .empty-messages h4 {
        font-size: 1.3rem;
        color: var(--dark);
        margin-bottom: 0.5rem;
    }
    
    .empty-messages p {
        color: var(--gray);
    }
    
    .messages-info {
        margin-bottom: 2rem;
    }
    
    .info-card {
        background: var(--white);
        border-radius: var(--radius);
        box-shadow: var(--shadow);
        padding: 1.5rem;
    }
    
    .info-card h3 {
        font-size: 1.3rem;
        color: var(--dark);
        margin-bottom: 1.5rem;
    }
    
    .info-list {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
        gap: 1.5rem;
    }
    
    .info-item {
        display: flex;
        gap: 1rem;
    }
    
    .info-icon {
        width: 40px;
        height: 40px;
        background: var(--light);
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1.2rem;
        flex-shrink: 0;
    }
    
    .info-content h4 {
        font-size: 1.1rem;
        color: var(--dark);
        margin-bottom: 0.5rem;
    }
    
    .info-content p {
        color: var(--gray);
        line-height: 1.5;
    }
    
    /* Responsive */
    @media (max-width: 768px) {
        .page-header h1 {
            font-size: 2rem;
        }
        
        .messages-container {
            grid-template-columns: 1fr;
        }
        
        .info-list {
            grid-template-columns: 1fr;
        }
    }