:root {
    --bg-color: #fafafa;
    --text-primary: #111827;
    --text-secondary: #4b5563;
    --border-color: #e5e7eb;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --panel-bg: #ffffff;
    --success: #059669;
    --error: #dc2626;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 3rem 1rem;
    line-height: 1.5;
}

.container {
    width: 100%;
    max-width: 700px;
}

.header {
    text-align: center;
    margin-bottom: 2.5rem;
}

.header h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
    letter-spacing: -0.025em;
}

.header p {
    color: var(--text-secondary);
    font-size: 1rem;
}

.glass-panel {
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 2rem;
    margin-bottom: 1.5rem;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
}

.form-group {
    margin-bottom: 1.25rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.625rem 0.875rem;
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-primary);
    font-family: inherit;
    font-size: 0.9375rem;
    transition: border-color 0.15s ease;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary);
}

/* Hide product and billNumber for 'balance' type dynamically via JS */
.hidden {
    display: none;
}

.btn-primary {
    width: 100%;
    padding: 0.75rem 1rem;
    background-color: var(--primary);
    color: #ffffff;
    border: none;
    border-radius: 6px;
    font-size: 0.9375rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.15s ease;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
}

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

/* Loader */
.loader {
    width: 16px;
    height: 16px;
    border: 2px solid rgba(255,255,255,0.4);
    border-radius: 50%;
    border-top-color: white;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Response Panel */
.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.panel-header h2 {
    font-size: 1.125rem;
    font-weight: 600;
}

.badge {
    padding: 0.25rem 0.625rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 500;
    background-color: #f3f4f6;
    color: var(--text-secondary);
}

.badge.success {
    background-color: #d1fae5;
    color: var(--success);
}

.badge.error {
    background-color: #fee2e2;
    color: var(--error);
}

.code-container {
    background-color: #f8fafc;
    border-radius: 6px;
    padding: 1.25rem;
    overflow-x: auto;
    border: 1px solid var(--border-color);
}

pre {
    margin: 0;
    font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    font-size: 0.875rem;
    color: var(--text-primary);
    white-space: pre-wrap;
    word-wrap: break-word;
}