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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.header {
    text-align: center;
    margin-bottom: 3rem;
    color: white;
}

.title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
    font-weight: 400;
}

.main-content {
    flex: 1;
}

.tip-card {
    background: white;
    border-radius: 16px;
    padding: 2rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    text-align: center;
}

.card-header {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.icon {
    font-size: 2.5rem;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: linear-gradient(135deg, #0084ff 0%, #0056b3 100%);
}

.card-header h2 {
    font-size: 1.5rem;
    font-weight: 600;
    color: #333;
}

.card-content p {
    color: #666;
    margin-bottom: 1.5rem;
    font-size: 0.95rem;
}

.amount-options {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    margin-bottom: 1rem;
    justify-content: center;
}

.amount-btn {
    padding: 0.75rem 1rem;
    border: 2px solid #e2e8f0;
    background: white;
    border-radius: 8px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 0.9rem;
    width: 220px;
    text-align: left;
    white-space: nowrap;
    display: inline-flex;
    justify-content: flex-start;
    align-items: center;
    position: relative;
    overflow: hidden;
}

.amount-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(0, 132, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.amount-btn:hover::before {
    left: 100%;
}

.amount-btn:hover {
    border-color: #0084ff;
    background: #f7fafc;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 132, 255, 0.2);
}

.amount-btn.selected {
    background: #0084ff;
    color: white;
    border-color: #0084ff;
    transform: scale(1.05);
    box-shadow: 0 6px 20px rgba(0, 132, 255, 0.3);
}

.amount-btn.selected::after {
    content: '✓';
    position: absolute;
    right: 10px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.2rem;
    animation: checkmark 0.3s ease;
}

@keyframes checkmark {
    0% {
        transform: translateY(-50%) scale(0) rotate(-45deg);
    }
    50% {
        transform: translateY(-50%) scale(1.2) rotate(10deg);
    }
    100% {
        transform: translateY(-50%) scale(1) rotate(0deg);
    }
}

.caffeine-meter {
    margin: 1.5rem 0;
    padding: 1rem;
    background: #f8f9fa;
    border-radius: 8px;
    border: 2px solid #e2e8f0;
}

.meter-label {
    font-weight: 600;
    color: #333;
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
}

.meter-bar {
    width: 100%;
    height: 20px;
    background: #e2e8f0;
    border-radius: 10px;
    overflow: hidden;
    margin-bottom: 0.5rem;
}

.meter-fill {
    height: 100%;
    background: linear-gradient(90deg, #6F4E37 0%, #8B4513 100%);
    border-radius: 10px;
    transition: width 0.8s ease;
    position: relative;
}

.meter-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
    animation: shimmer 2s infinite;
}

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

.meter-text {
    font-size: 0.8rem;
    color: #666;
    text-align: center;
    font-weight: 500;
}

.custom-amount {
    background: linear-gradient(135deg, #0084ff 0%, #0056b3 100%);
    color: white;
    border: none;
}

.custom-amount:hover {
    background: linear-gradient(135deg, #0056b3 0%, #003d82 100%);
}

.custom-amount-input {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-top: 1rem;
    justify-content: center;
}

.custom-amount-input input {
    padding: 0.75rem;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
}

.custom-amount-input input:focus {
    outline: none;
    border-color: #0084ff;
}

.custom-amount-input span {
    font-weight: 500;
    color: #666;
}

.venmo-info {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid #e2e8f0;
}

.venmo-info h3 {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: #333;
}

.tip-summary {
    margin-bottom: 1.5rem;
    font-size: 1.2rem;
}

.tip-item-name {
    font-size: 0.8rem;
    font-weight: 400;
    color: #666;
    opacity: 0.8;
}

.tip-amount {
    font-weight: 700;
    font-size: 1.4rem;
    color: #0084ff;
}

.venmo-details {
    margin-bottom: 1.5rem;
}

.venmo-details p {
    margin-bottom: 1rem;
    font-weight: 500;
    color: #333;
}

.venmo-username {
    display: flex;
    gap: 0.75rem;
    align-items: center;
    justify-content: center;
    margin-bottom: 1.5rem;
}

.username-text {
    font-size: 1.1rem;
    font-weight: 600;
    color: #333;
    background: #f8f9fa;
    padding: 0.75rem 1.25rem;
    border-radius: 8px;
    border: 2px solid #e2e8f0;
    font-family: 'Courier New', monospace;
}

.copy-btn {
    background: #0084ff;
    color: white;
    border: none;
    padding: 0.75rem 1.25rem;
    border-radius: 8px;
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s ease;
    white-space: nowrap;
}

.copy-btn:hover {
    background: #0056b3;
    transform: translateY(-1px);
}

.venmo-btn {
    background: linear-gradient(135deg, #0084ff 0%, #0056b3 100%);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease;
    margin-bottom: 1.5rem;
    min-width: 150px;
}

.venmo-btn:hover {
    transform: translateY(-2px);
}

.thank-you-message {
    text-align: center;
    font-size: 1.05rem;
    font-weight: 500;
    color: #0084ff;
    background: linear-gradient(135deg, #f7fafc 0%, #e2e8f0 100%);
    padding: 1.25rem;
    border-radius: 8px;
    border-left: 4px solid #0084ff;
    margin-top: 0;
}

.footer {
    text-align: center;
    margin-top: 2rem;
    color: white;
    font-size: 1.1rem;
}

@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }
    
    .title {
        font-size: 2rem;
    }
    
    .tip-card {
        padding: 1.5rem;
    }
    
    .amount-options {
        justify-content: center;
    }
    
    .amount-btn {
        width: 200px;
        font-size: 0.85rem;
    }
}