*styles.css*

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #2d3748;
}

.container {
    max-width: 420px;
    margin: 0 auto;
    background: white;
    min-height: 100vh;
    box-shadow: 0 0 30px rgba(0,0,0,0.1);
    position: relative;
    overflow-x: hidden;
}

/* Responsive adjustments */
@media (min-width: 768px) {
    .container {
        max-width: 500px;
        margin: 20px auto;
        min-height: calc(100vh - 40px);
        border-radius: 20px;
    }
}

@media (min-width: 1024px) {
    .container {
        max-width: 600px;
    }
}

.header {
    background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%);
    padding: 20px;
    text-align: center;
    position: relative;
}

@media (min-width: 768px) {
    .header {
        padding: 30px;
        border-radius: 20px 20px 0 0;
    }
}

.logo {
    font-size: 28px;
    font-weight: 700;
    color: #4a5568;
    margin-bottom: 8px;
}

@media (min-width: 768px) {
    .logo {
        font-size: 32px;
    }
}

.tagline {
    color: #718096;
    font-size: 14px;
}

@media (min-width: 768px) {
    .tagline {
        font-size: 16px;
    }
}

.page {
    display: none;
    padding: 20px;
    animation: slideIn 0.3s ease-out;
}

@media (min-width: 768px) {
    .page {
        padding: 30px;
    }
}

.page.active {
    display: block;
}

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

.card {
    background: white;
    border-radius: 16px;
    padding: 24px;
    margin-bottom: 16px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.08);
    border: 1px solid #e2e8f0;
}

@media (min-width: 768px) {
    .card {
        padding: 30px;
        margin-bottom: 20px;
    }
}

.form-group {
    margin-bottom: 20px;
}

@media (min-width: 768px) {
    .form-group {
        margin-bottom: 24px;
    }
}

.form-label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #4a5568;
    font-size: 14px;
}

@media (min-width: 768px) {
    .form-label {
        font-size: 16px;
        margin-bottom: 10px;
    }
}

.form-input {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    font-size: 16px;
    transition: all 0.3s ease;
    background: #f7fafc;
}

@media (min-width: 768px) {
    .form-input {
        padding: 16px 20px;
        font-size: 18px;
    }
}

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

.btn {
    width: 100%;
    padding: 16px;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

@media (min-width: 768px) {
    .btn {
        padding: 18px;
        font-size: 18px;
    }
}

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

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
}

.btn-secondary {
    background: #f7fafc;
    color: #4a5568;
    border: 2px solid #e2e8f0;
}

.btn-secondary:hover {
    background: #edf2f7;
    border-color: #cbd5e0;
}

.btn-small {
    width: auto;
    padding: 8px 16px;
    font-size: 14px;
    margin: 4px;
}

@media (min-width: 768px) {
    .btn-small {
        padding: 10px 20px;
        font-size: 16px;
    }
}

.friends-list {
    margin-top: 16px;
}

.friend-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 16px;
    background: #f7fafc;
    border-radius: 8px;
    margin-bottom: 8px;
    border: 1px solid #e2e8f0;
}

@media (min-width: 768px) {
    .friend-item {
        padding: 16px 20px;
    }
}

.friend-amount {
    font-weight: 600;
    color: #667eea;
}

.split-options {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    margin-bottom: 20px;
}

@media (min-width: 768px) {
    .split-options {
        gap: 16px;
        margin-bottom: 24px;
    }
}

.split-option {
    padding: 16px;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: #f7fafc;
}

@media (min-width: 768px) {
    .split-option {
        padding: 20px;
    }
}

.split-option.active {
    border-color: #667eea;
    background: rgba(102, 126, 234, 0.1);
}

.split-option i {
    font-size: 24px;
    margin-bottom: 8px;
    color: #667eea;
}

@media (min-width: 768px) {
    .split-option i {
        font-size: 28px;
    }
}

.bill-summary {
    background: #f0fff4;
    border: 2px solid #9ae6b4;
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 20px;
}

@media (min-width: 768px) {
    .bill-summary {
        padding: 24px;
        margin-bottom: 24px;
    }
}

.bill-title {
    font-size: 18px;
    font-weight: 700;
    color: #22543d;
    margin-bottom: 8px;
}

@media (min-width: 768px) {
    .bill-title {
        font-size: 22px;
    }
}

.bill-total {
    font-size: 24px;
    font-weight: 700;
    color: #38a169;
    margin-bottom: 16px;
}

@media (min-width: 768px) {
    .bill-total {
        font-size: 28px;
    }
}

.payment-status {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
}

@media (min-width: 768px) {
    .payment-status {
        font-size: 14px;
        padding: 10px 16px;
    }
}

.status-paid {
    background: #c6f6d5;
    color: #22543d;
}

.status-pending {
    background: #fed7d7;
    color: #742a2a;
}

.share-link {
    background: #e6fffa;
    border: 2px solid #81e6d9;
    border-radius: 12px;
    padding: 16px;
    margin-bottom: 20px;
}

@media (min-width: 768px) {
    .share-link {
        padding: 20px;
        margin-bottom: 24px;
    }
}

.share-link input {
    background: transparent;
    border: none;
    width: 100%;
    font-size: 14px;
    color: #2d3748;
}

@media (min-width: 768px) {
    .share-link input {
        font-size: 16px;
    }
}

.share-link input:focus {
    outline: none;
}

.share-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 8px;
    margin-top: 12px;
}

@media (min-width: 768px) {
    .share-buttons {
        gap: 12px;
        margin-top: 16px;
    }
}

.btn-share {
    padding: 10px;
    border: none;
    border-radius: 8px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

@media (min-width: 768px) {
    .btn-share {
        padding: 12px;
        font-size: 14px;
    }
}

.btn-whatsapp {
    background: #25d366;
    color: white;
}

.btn-instagram {
    background: #e4405f;
    color: white;
}

.btn-email {
    background: #4285f4;
    color: white;
}

.back-btn {
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(255,255,255,0.9);
    border: none;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    color: #4a5568;
}

@media (min-width: 768px) {
    .back-btn {
        width: 45px;
        height: 45px;
        font-size: 20px;
    }
}

.tab-bar {
    position: fixed;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: 420px;
    background: white;
    border-top: 1px solid #e2e8f0;
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    z-index: 100;
}

@media (min-width: 768px) {
    .tab-bar {
        max-width: 500px;
        border-radius: 0 0 20px 20px;
    }
}

@media (min-width: 1024px) {
    .tab-bar {
        max-width: 600px;
    }
}

.tab-item {
    padding: 16px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: white;
    border: none;
}

@media (min-width: 768px) {
    .tab-item {
        padding: 20px;
    }
}

.tab-item.active {
    background: rgba(102, 126, 234, 0.1);
    color: #667eea;
}

.tab-item i {
    font-size: 20px;
    margin-bottom: 4px;
    display: block;
}

@media (min-width: 768px) {
    .tab-item i {
        font-size: 24px;
    }
}

.tab-item span {
    font-size: 12px;
    font-weight: 600;
}

@media (min-width: 768px) {
    .tab-item span {
        font-size: 14px;
    }
}

.home-actions {
    margin-top: 20px;
}

.quick-action {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 20px;
    background: white;
    border-radius: 16px;
    margin-bottom: 12px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.05);
    cursor: pointer;
    transition: all 0.3s ease;
    border: 1px solid #e2e8f0;
}

@media (min-width: 768px) {
    .quick-action {
        padding: 24px;
        margin-bottom: 16px;
        gap: 20px;
    }
}

.quick-action:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}

.quick-action-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    flex-shrink: 0;
}

@media (min-width: 768px) {
    .quick-action-icon {
        width: 56px;
        height: 56px;
        font-size: 24px;
    }
}

.action-food {background: #fed7e2; color: #b83280;}
.action-travel {background: #bee3f8; color: #3182ce;}
.action-streaming {background: #c6f6d5; color: #38a169;}
.action-custom {background: #faf089; color: #b7791f;}

.recent-bills {
    margin-top: 24px;
}

@media (min-width: 768px) {
    .recent-bills {
        margin-top: 30px;
    }
}

.section-title {
    font-size: 18px;
    font-weight: 700;
    color: #2d3748;
    margin-bottom: 16px;
}

@media (min-width: 768px) {
    .section-title {
        font-size: 22px;
        margin-bottom: 20px;
    }
}

.bill-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px;
    background: white;
    border-radius: 12px;
    margin-bottom: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
    border: 1px solid #e2e8f0;
    cursor: pointer;
}

@media (min-width: 768px) {
    .bill-item {
        padding: 20px;
        margin-bottom: 12px;
    }
}

.bill-info h4 {
    font-weight: 600;
    margin-bottom: 4px;
}

@media (min-width: 768px) {
    .bill-info h4 {
        font-size: 18px;
    }
}

.bill-info p {
    font-size: 12px;
    color: #718096;
}

@media (min-width: 768px) {
    .bill-info p {
        font-size: 14px;
    }
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: #718096;
}

@media (min-width: 768px) {
    .empty-state {
        padding: 80px 20px;
    }
}

.empty-state i {
    font-size: 48px;
    margin-bottom: 16px;
    opacity: 0.5;
}

@media (min-width: 768px) {
    .empty-state i {
        font-size: 64px;
        margin-bottom: 20px;
    }
}

.main-content {
    padding-bottom: 80px;
}

@media (min-width: 768px) {
    .main-content {
        padding-bottom: 100px;
    }
}

.notification {
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    background: #48bb78;
    color: white;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: 600;
    z-index: 1000;
    opacity: 0;
    transition: all 0.3s ease;
    max-width: 90%;
    text-align: center;
}

@media (min-width: 768px) {
    .notification {
        padding: 16px 32px;
        font-size: 16px;
        max-width: 400px;
    }
}

.notification.show {
    opacity: 1;
}

/* Additional responsive improvements */
@media (max-width: 480px) {
    .container {
        max-width: 100%;
    }
    
    .page {
        padding: 15px;
    }
    
    .quick-action {
        padding: 16px;
    }
    
    .card {
        padding: 20px;
    }
}

/* Hover effects for desktop */
@media (min-width: 768px) {
    .btn:hover {
        transform: translateY(-2px);
    }
    
    .bill-item:hover {
        transform: translateY(-2px);
        box-shadow: 0 4px 16px rgba(0,0,0,0.1);
    }
    
    .tab-item:hover:not(.active) {
        background: rgba(102, 126, 234, 0.05);
    }
}