/* Reset và base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    overflow: hidden;
}

.header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 30px;
    text-align: center;
}

.header h1 {
    font-size: 2.5rem;
    font-weight: 300;
    margin-bottom: 10px;
}

.header p {
    opacity: 0.9;
    font-size: 1.1rem;
}

.content {
    padding: 30px;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 12px 24px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-decoration: none;
    border-radius: 25px;
    transition: all 0.3s ease;
    border: none;
    cursor: pointer;
    font-size: 16px;
    font-weight: 500;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-danger {
    background: linear-gradient(135deg, #ff6b6b 0%, #ee5a24 100%);
    padding: 8px 16px;
    font-size: 14px;
}

.btn-danger:hover {
    box-shadow: 0 5px 15px rgba(255, 107, 107, 0.4);
}

/* Form styles */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #555;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid #e1e5e9;
    border-radius: 8px;
    font-size: 16px;
    transition: border-color 0.3s ease;
    font-family: inherit;
}

.form-control:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

textarea.form-control {
    resize: vertical;
    min-height: 120px;
}

/* Message list */
.message-list {
    margin-top: 30px;
}

.message-item {
    background: #f8f9fa;
    border-left: 4px solid #667eea;
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 0 8px 8px 0;
    transition: all 0.3s ease;
    position: relative;
}

.message-item:hover {
    transform: translateX(5px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.message-author {
    font-weight: 600;
    color: #667eea;
    font-size: 1.1rem;
    margin-bottom: 8px;
}

.message-content {
    color: #555;
    line-height: 1.6;
    margin-bottom: 10px;
}

.message-actions {
    text-align: right;
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: #666;
}

.empty-state p {
    font-size: 1.2rem;
    margin-bottom: 20px;
}

/* Error messages */
.error {
    background: #ffe6e6;
    color: #d63031;
    padding: 12px 16px;
    border-radius: 8px;
    border-left: 4px solid #d63031;
    margin-bottom: 20px;
}

/* Navigation */
.nav {
    text-align: center;
    margin-bottom: 30px;
}

/* Responsive */
@media (max-width: 768px) {
    body {
        padding: 10px;
    }
    
    .header h1 {
        font-size: 2rem;
    }
    
    .content {
        padding: 20px;
    }
    
    .message-item {
        padding: 15px;
    }
}

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

.message-item {
    animation: fadeIn 0.5s ease-out;
}

/* Loading state */
.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.btn:disabled:hover {
    transform: none;
    box-shadow: none;
}