:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --secondary: #10b981;
    --accent: #f59e0b;
    --dark: #0f172a;
    --muted: #64748b;
    --border: #dbe3ef;
    --bg: #f8fafc;
    --white: #ffffff;
    --shadow-lg: 0 18px 40px rgba(15, 23, 42, 0.12);
    --radius: 18px;
}

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

body {
    font-family: 'Inter', sans-serif;
    color: var(--dark);
    background:
        radial-gradient(circle at 8% 8%, rgba(37, 99, 235, 0.08), transparent 32%),
        radial-gradient(circle at 92% 90%, rgba(16, 185, 129, 0.08), transparent 28%),
        var(--bg);
    line-height: 1.6;
}

.container {
    width: min(1120px, 92%);
    margin: 0 auto;
}

.checkout-header {
    border-bottom: 1px solid rgba(37, 99, 235, 0.16);
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(8px);
    position: sticky;
    top: 0;
    z-index: 10;
}

.checkout-header .container {
    min-height: 72px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
}

.brand {
    text-decoration: none;
    font-family: 'Poppins', sans-serif;
    font-size: 1.45rem;
    font-weight: 800;
    color: var(--dark);
    display: inline-flex;
    align-items: center;
    gap: 10px;
}

.brand i {
    color: var(--primary);
}

.back-link {
    text-decoration: none;
    color: var(--primary-dark);
    font-weight: 600;
}

.checkout-main {
    padding: 56px 0;
}

.checkout-layout {
    display: grid;
    grid-template-columns: 1.35fr 1fr;
    gap: 26px;
    align-items: start;
}

.checkout-card,
.summary-card {
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    padding: 28px;
}

.checkout-card h1 {
    font-family: 'Poppins', sans-serif;
    font-size: clamp(1.5rem, 2.8vw, 2.15rem);
    margin-bottom: 8px;
}

.subtitle {
    color: var(--muted);
    margin-bottom: 24px;
}

.form-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.form-group.full {
    grid-column: 1 / -1;
}

.form-group label {
    font-size: 0.92rem;
    font-weight: 600;
    color: #334155;
}

.form-group input,
.form-group textarea {
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 11px 12px;
    font-size: 0.98rem;
    font-family: 'Inter', sans-serif;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: #93c5fd;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.14);
}

.note {
    margin-top: 12px;
    color: #475569;
    font-size: 0.9rem;
}

.pay-btn {
    margin-top: 18px;
    border: 0;
    width: 100%;
    border-radius: 999px;
    padding: 13px 18px;
    color: #fff;
    background: linear-gradient(135deg, #2563eb, #1d4ed8);
    font-weight: 700;
    font-size: 1rem;
    cursor: pointer;
    transition: 0.25s ease;
}

.pay-btn:hover {
    transform: translateY(-1px);
}

.pay-btn:disabled {
    opacity: 0.75;
    cursor: not-allowed;
}

.summary-card h2 {
    font-family: 'Poppins', sans-serif;
    font-size: 1.22rem;
    margin-bottom: 16px;
}

.summary-list {
    list-style: none;
    display: grid;
    gap: 12px;
}

.summary-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    border-bottom: 1px solid #edf2f7;
    padding-bottom: 11px;
}

.summary-item span {
    color: #475569;
}

.summary-item strong {
    color: var(--dark);
}

.summary-total {
    margin-top: 16px;
    padding-top: 14px;
    border-top: 1px dashed #cbd5e1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 1.05rem;
    font-weight: 700;
}

.benefits {
    margin-top: 20px;
    list-style: none;
    display: grid;
    gap: 10px;
}

.benefits li {
    color: #334155;
    font-size: 0.95rem;
    padding-left: 24px;
    position: relative;
}

.benefits li::before {
    content: '\f058';
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    color: var(--secondary);
    position: absolute;
    left: 0;
    top: 2px;
}

.success-box {
    margin-top: 18px;
    background: #f0fdf4;
    border: 1px solid #86efac;
    border-radius: 12px;
    padding: 14px;
    color: #14532d;
    display: none;
}

.success-box strong {
    display: block;
    margin-bottom: 4px;
}

@media (max-width: 960px) {
    .checkout-layout {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .checkout-main {
        padding: 36px 0;
    }

    .form-grid {
        grid-template-columns: 1fr;
    }

    .checkout-card,
    .summary-card {
        padding: 20px;
    }
}