/* Reset và Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

.container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    padding: 30px;
}

h1 {
    text-align: center;
    color: #333;
    margin-bottom: 30px;
    font-size: 2.5em;
    font-weight: 700;
}

/* Header Section */
.header-section {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid #e9ecef;
}

.header-section h1 {
    margin: 0;
    flex: 1;
}

.settings-button {
    background: linear-gradient(135deg, #6c757d 0%, #495057 100%);
    color: white;
    text-decoration: none;
    padding: 12px 20px;
    border-radius: 10px;
    font-weight: 600;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.settings-button:hover {
    background: linear-gradient(135deg, #5a6268 0%, #3d4142 100%);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
    color: white;
}

h2 {
    color: #555;
    margin-bottom: 20px;
    font-size: 1.5em;
}

/* App Selection Styles */
.app-selection {
    margin-bottom: 30px;
}

.app-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.app-card {
    background: #f8f9fa;
    border: 2px solid #e9ecef;
    border-radius: 15px;
    padding: 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
}

.app-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    border-color: #667eea;
}

.app-card.selected {
    border-color: #667eea;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.app-card.selected::after {
    content: "✓";
    position: absolute;
    top: 10px;
    right: 10px;
    background: #28a745;
    color: white;
    border-radius: 50%;
    width: 25px;
    height: 25px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 14px;
}

.app-icon {
    width: 60px;
    height: 60px;
    border-radius: 15px;
    margin-bottom: 15px;
    object-fit: cover;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
    background: #f8f9fa;
}

.app-icon:error {
    background: #e9ecef;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    color: #6c757d;
}

.app-icon:error::before {
    content: "📱";
}

.app-card:hover .app-icon {
    transform: scale(1.1);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.app-card.selected .app-icon {
    box-shadow: 0 4px 12px rgba(255, 255, 255, 0.3);
}

/* Brand-specific hover effects */
.app-card[data-app="zalopay"]:hover {
    border-color: #0068FF;
}

.app-card[data-app="momo"]:hover {
    border-color: #D82D8B;
}

.app-card[data-app="viettelpay"]:hover {
    border-color: #F57C00;
}

.app-card[data-app="vnpay"]:hover {
    border-color: #1976D2;
}

.app-card[data-app="shopepay"]:hover {
    border-color: #EE4D2D;
}

.app-card h3 {
    margin-bottom: 10px;
    font-size: 1.2em;
    font-weight: 600;
}

.app-card p {
    font-size: 0.9em;
    opacity: 0.8;
}

.app-card.selected p {
    opacity: 1;
}

/* Current Selection Styles */
.current-selection {
    background: #f8f9fa;
    border-radius: 10px;
    padding: 20px;
    margin-bottom: 30px;
    text-align: center;
}

.current-selection h3 {
    color: #333;
    font-size: 1.3em;
}

#current-app {
    color: #667eea;
    font-weight: 600;
}

/* Button Styles */
.actions {
    text-align: center;
    margin-bottom: 30px;
}

.btn-primary, .btn-secondary {
    padding: 15px 30px;
    border: none;
    border-radius: 10px;
    font-size: 1.1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin: 0 10px;
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:disabled {
    background: #ccc;
    cursor: not-allowed;
    transform: none;
}

.btn-secondary {
    background: #6c757d;
    color: white;
}

.btn-secondary:hover {
    background: #5a6268;
    transform: translateY(-2px);
}

/* Info Section */
.info {
    background: #e3f2fd;
    border-left: 4px solid #2196f3;
    padding: 15px;
    border-radius: 5px;
    margin-top: 20px;
}

.info p {
    color: #1565c0;
    margin: 0;
}

/* Loading Animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid #f3f3f3;
    border-top: 3px solid #667eea;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-left: 10px;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 20px;
        margin: 10px;
    }
    
    .header-section {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    .header-section h1 {
        font-size: 2em;
    }
    
    .settings-button {
        align-self: center;
        padding: 10px 18px;
        font-size: 0.9em;
    }
    
    .app-grid {
        grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
        gap: 15px;
    }
    
    .app-card {
        padding: 15px;
    }
    
    .app-icon {
        width: 50px;
        height: 50px;
    }
    
    .btn-primary, .btn-secondary {
        padding: 12px 25px;
        font-size: 1em;
        margin: 5px;
    }
}

/* Animation for app cards */
.app-card {
    animation: slideIn 0.5s ease-out;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Toast notification */
.toast {
    position: fixed;
    top: 20px;
    right: 20px;
    background: #28a745;
    color: white;
    padding: 15px 20px;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    z-index: 1000;
    animation: slideInRight 0.3s ease-out;
}

.toast.error {
    background: #dc3545;
}

.toast.info {
    background: #17a2b8;
}

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