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

:root {
    --verizon-primary: #bf1111;
    --verizon-contrast: #000000;
    --verizon-primary-rgb: 191, 17, 17;
    --verizon-contrast-rgb: 0, 0, 0;
    --ups-primary: #FFB500;
    --ups-contrast: #351C15;
    --ups-primary-rgb: 255, 181, 0;
    --ups-contrast-rgb: 53, 28, 21;

    --primary-color: var(--verizon-primary);
    --primary-dark: var(--verizon-contrast);
    --secondary-color: var(--verizon-contrast);
    --background: #f5f5f5;
    --card-background: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --border-color: #dddddd;
    --success-color: #00ab44;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 4px 16px rgba(0, 0, 0, 0.15);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: radial-gradient(circle at top, #ffffff 0%, #f3f3f3 40%, #e7e7e7 100%);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 40px 20px;
    min-height: 100vh;
}

.container {
    max-width: 960px;
    margin: 0 auto;
    background: var(--card-background);
    border-radius: 20px;
    box-shadow: 0 25px 60px rgba(0, 0, 0, 0.12);
    overflow: hidden;
    border: 1px solid rgba(255, 255, 255, 0.6);
}

header {
    background: linear-gradient(135deg, var(--verizon-primary) 0%, rgba(0, 0, 0, 0.9) 100%);
    color: white;
    padding: 48px 40px;
    text-align: center;
    position: relative;
    z-index: 0;
}

header::after {
    content: '';
    position: absolute;
    inset: 0;
    background: url('data:image/svg+xml,%3Csvg width="160" height="160" viewBox="0 0 160 160" xmlns="http://www.w3.org/2000/svg"%3E%3Cpath d="M0 120L40 160H0zM160 40V0h-40z" fill="rgba(255,255,255,0.08)"/%3E%3C/svg%3E');
    opacity: 0.6;
    pointer-events: none;
    z-index: -1;
}

header > * {
    position: relative;
    z-index: 1;
}

header h1 {
    font-size: 2.4rem;
    margin-bottom: 12px;
    letter-spacing: 0.5px;
}

.subtitle {
    font-size: 1.05rem;
    opacity: 0.95;
}

.tabs {
    display: flex;
    background: #e8e8e8;
    border-bottom: 1px solid var(--border-color);
    padding: 0;
    gap: 0;
}

.tab-button {
    flex: 1;
    padding: 18px 24px;
    background: transparent;
    border: none;
    border-right: 1px solid #d0d0d0;
    font-size: 1.05rem;
    font-weight: 600;
    color: #666666;
    cursor: pointer;
    transition: all 0.25s ease;
    position: relative;
    outline: none;
    --tab-btn-primary: var(--primary-color);
    --tab-btn-contrast: #ffffff;
    --tab-btn-shadow: rgba(var(--verizon-primary-rgb), 0.25);
    --tab-btn-hover: rgba(255, 255, 255, 0.5);
}

.tab-button:last-child {
    border-right: none;
}

.tab-button:hover:not(.active),
.tab-button:focus-visible:not(.active) {
    background: var(--tab-btn-hover);
    color: var(--tab-btn-primary);
}

.tab-button:focus-visible {
    outline: 3px solid var(--tab-btn-primary);
    outline-offset: -3px;
}

.tab-button.active {
    background: var(--tab-btn-primary);
    color: var(--tab-btn-contrast);
    border-bottom: 4px solid var(--tab-btn-contrast);
    font-weight: 700;
    box-shadow: inset 0 -4px 0 0 var(--tab-btn-shadow);
}

.tab-button[data-tab="verizon"] {
    color: rgba(var(--verizon-contrast-rgb), 0.75);
    --tab-btn-primary: var(--verizon-primary);
    --tab-btn-contrast: var(--verizon-contrast);
    --tab-btn-shadow: rgba(var(--verizon-primary-rgb), 0.35);
    --tab-btn-hover: rgba(191, 17, 17, 0.12);
}

.tab-button[data-tab="verizon"].active {
    color: var(--tab-btn-contrast);
}

.tab-button[data-tab="ups"] {
    color: rgba(var(--ups-contrast-rgb), 0.8);
    --tab-btn-primary: var(--ups-primary);
    --tab-btn-contrast: var(--ups-contrast);
    --tab-btn-shadow: rgba(var(--ups-contrast-rgb), 0.25);
    --tab-btn-hover: rgba(255, 181, 0, 0.2);
}

.tab-button[data-tab="ups"].active {
    color: var(--tab-btn-contrast);
}

.tab-content {
    display: none;
    --tab-primary: var(--primary-color);
    --tab-primary-dark: var(--primary-dark);
    --tab-contrast: var(--primary-dark);
    --tab-on-primary: #ffffff;
    --tab-on-primary-contrast: #ffffff;
    --tab-primary-rgb: var(--verizon-primary-rgb);
    --tab-contrast-rgb: var(--verizon-contrast-rgb);
    --tab-surface: rgba(var(--tab-primary-rgb), 0.08);
    --tab-border: rgba(var(--tab-primary-rgb), 0.4);
    --tab-border-soft: rgba(var(--tab-primary-rgb), 0.18);
    --tab-shadow: rgba(var(--tab-primary-rgb), 0.2);
    --tab-shadow-strong: rgba(var(--tab-primary-rgb), 0.3);
}

.tab-content.active {
    display: block;
}

#verizon-content {
    --tab-primary: var(--verizon-primary);
    --tab-primary-dark: var(--verizon-contrast);
    --tab-contrast: var(--verizon-contrast);
    --tab-on-primary: var(--verizon-contrast);
    --tab-on-primary-contrast: var(--verizon-primary);
    --tab-primary-rgb: var(--verizon-primary-rgb);
    --tab-contrast-rgb: var(--verizon-contrast-rgb);
    --tab-surface: rgba(var(--verizon-primary-rgb), 0.08);
    --tab-border: rgba(var(--verizon-primary-rgb), 0.45);
    --tab-border-soft: rgba(var(--verizon-primary-rgb), 0.22);
    --tab-shadow: rgba(var(--verizon-primary-rgb), 0.24);
    --tab-shadow-strong: rgba(var(--verizon-primary-rgb), 0.32);
}

#ups-content {
    --tab-primary: var(--ups-primary);
    --tab-primary-dark: var(--ups-contrast);
    --tab-contrast: var(--ups-contrast);
    --tab-on-primary: var(--ups-contrast);
    --tab-on-primary-contrast: var(--ups-primary);
    --tab-primary-rgb: var(--ups-primary-rgb);
    --tab-contrast-rgb: var(--ups-contrast-rgb);
    --tab-surface: rgba(var(--ups-primary-rgb), 0.18);
    --tab-border: rgba(var(--ups-contrast-rgb), 0.35);
    --tab-border-soft: rgba(var(--ups-primary-rgb), 0.28);
    --tab-shadow: rgba(var(--ups-contrast-rgb), 0.25);
    --tab-shadow-strong: rgba(var(--ups-contrast-rgb), 0.35);
}

main {
    display: grid;
    gap: 40px;
    padding: 40px;
    background: linear-gradient(180deg, rgba(248, 248, 248, 0.9) 0%, rgba(238, 238, 238, 0.9) 100%);
}

.form-group {
    margin-bottom: 25px;
}

.form-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.input-with-symbol {
    position: relative;
    display: flex;
    align-items: center;
}

.currency-symbol {
    position: absolute;
    left: 15px;
    font-size: 1.1rem;
    color: var(--text-secondary);
    font-weight: 600;
}

input[type="text"],
input[type="number"],
select {
    width: 100%;
    padding: 12px 15px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: all 0.3s ease;
}

.input-with-symbol input {
    padding-left: 35px;
}

input:focus,
select:focus {
    outline: none;
    border-color: var(--tab-primary);
    box-shadow: 0 0 0 3px rgba(var(--tab-primary-rgb), 0.15);
}

.charges-section {
    margin: 30px 0;
    padding: 25px;
    background: var(--tab-surface);
    border-radius: 12px;
    border: 1px dashed var(--tab-border);
}

.charges-section.balanced {
    background: rgba(0, 171, 68, 0.08);
    border-color: rgba(0, 171, 68, 0.5);
}

.charges-section h3 {
    margin-bottom: 20px;
    color: var(--text-primary);
    font-size: 1.1rem;
}

.charge-item {
    display: grid;
    grid-template-columns: 1fr 1fr auto;
    gap: 15px;
    margin-bottom: 15px;
    padding: 18px;
    background: white;
    border-radius: 12px;
    box-shadow: var(--shadow);
    animation: slideIn 0.3s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.charge-item input,
.charge-item select {
    margin: 0;
}

.charge-item .remove-btn {
    background: #ff4444;
    color: white;
    border: none;
    border-radius: 6px;
    padding: 10px 15px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: background 0.3s ease;
}

.charge-item .remove-btn:hover {
    background: #cc0000;
}

.btn {
    padding: 14px 28px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-block;
    text-align: center;
}

.btn-primary {
    background: var(--tab-primary);
    color: var(--tab-on-primary);
    width: 100%;
    margin-top: 20px;
    box-shadow: 0 12px 24px var(--tab-shadow);
}

.btn-primary:hover {
    background: var(--tab-primary-dark);
    color: var(--tab-on-primary-contrast);
    transform: translateY(-2px);
    box-shadow: 0 16px 24px var(--tab-shadow-strong);
}

.btn-secondary {
    background: white;
    color: var(--tab-primary);
    border: 2px solid var(--tab-primary);
    margin-right: 10px;
}

.btn-secondary:hover {
    background: var(--tab-primary);
    color: var(--tab-on-primary);
}

.btn-outline {
    background: transparent;
    color: var(--text-secondary);
    border: 2px solid var(--border-color);
    margin-top: 12px;
}

.btn-outline:hover {
    border-color: var(--text-secondary);
    color: var(--text-primary);
}

#addChargeBtn {
    width: 100%;
    margin-top: 10px;
}

.results-section {
    margin-top: 40px;
    padding-top: 40px;
    border-top: 2px solid rgba(0, 0, 0, 0.05);
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.results-section h2 {
    margin-bottom: 20px;
    color: var(--tab-primary);
}

.results-container {
    background: white;
    padding: 28px;
    border-radius: 14px;
    margin-bottom: 24px;
    font-family: 'Source Code Pro', 'Courier New', monospace;
    white-space: pre-wrap;
    font-size: 0.95rem;
    line-height: 1.8;
    box-shadow: 0 16px 30px rgba(0, 0, 0, 0.08);
    border: 1px solid var(--tab-border-soft);
}

.result-line {
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
}

.result-line:last-child {
    border-bottom: none;
}

.result-line.header {
    font-weight: bold;
    color: var(--tab-primary);
    font-size: 1.05rem;
}

.result-line.main {
    font-weight: 600;
    color: var(--success-color);
}

.result-line.warning {
    color: var(--tab-primary-dark);
    font-weight: 600;
}

.input-section {
    background: white;
    padding: 32px;
    border-radius: 16px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.08);
    border: 1px solid var(--tab-border-soft);
}

.section-title {
    font-size: 1.4rem;
    margin-bottom: 8px;
    color: var(--tab-primary);
}

.section-description {
    color: var(--text-secondary);
    margin-bottom: 24px;
}

.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
    background: rgba(0, 171, 68, 0.08);
    border-radius: 12px;
    border: 1px solid rgba(0, 171, 68, 0.25);
}

.empty-state p {
    font-size: 1.05rem;
}

@media (max-width: 768px) {
    body {
        padding: 20px 10px;
    }

    header h1 {
        font-size: 1.8rem;
    }

    main {
        padding: 24px;
    }

    .charge-item {
        grid-template-columns: 1fr;
        gap: 10px;
    }

    .btn {
        padding: 12px 20px;
        font-size: 0.95rem;
    }
}