:root {
  --bg: #f1f5f9;
  --panel: #ffffff;
  --border: #e2e8f0;
  --ink: #0f172a;
  --muted: #64748b;
  --brand: #1f4e79;
  --brand-2: #2563eb;
  --ring: rgba(37, 99, 235, 0.25);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.5;
}

header {
  padding: 28px 24px 12px;
  max-width: 1100px;
  margin: 0 auto;
}

header h1 {
  margin: 0 0 4px;
  font-size: 22px;
}

header p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.layout {
  max-width: 1100px;
  margin: 0 auto;
  padding: 12px 24px 48px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 24px;
  align-items: start;
}

@media (max-width: 820px) {
  .layout {
    grid-template-columns: 1fr;
  }
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

.panel h2 {
  margin: 0 0 16px;
  font-size: 15px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
}

label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin: 16px 0 6px;
}

label:first-of-type {
  margin-top: 0;
}

.hint {
  font-weight: 400;
  color: var(--muted);
}

input[type="text"],
textarea,
select {
  width: 100%;
  padding: 10px 12px;
  font: inherit;
  font-size: 14px;
  color: var(--ink);
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  resize: vertical;
}

select {
  cursor: pointer;
}

input[type="text"]:focus,
textarea:focus,
select:focus {
  outline: none;
  border-color: var(--brand-2);
  box-shadow: 0 0 0 3px var(--ring);
}

textarea {
  min-height: 110px;
  line-height: 1.45;
}

.sizes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 18px;
}

@media (max-width: 480px) {
  .sizes {
    grid-template-columns: 1fr;
  }
}

.size-field label {
  margin: 0 0 6px;
}

.size-row {
  display: flex;
  align-items: center;
  gap: 10px;
}

.size-row input[type="range"] {
  flex: 1;
  min-width: 0;
  accent-color: var(--brand-2);
}

.size-row input[type="number"] {
  width: 64px;
  flex: 0 0 auto;
  padding: 6px 8px;
  font: inherit;
  font-size: 13px;
  border: 1px solid var(--border);
  border-radius: 6px;
}

.size-row input[type="number"]:focus {
  outline: none;
  border-color: var(--brand-2);
  box-shadow: 0 0 0 3px var(--ring);
}

.size-note {
  margin: 8px 0 0;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  margin: 16px 0 0;
  cursor: pointer;
}

.checkbox-row input {
  width: 16px;
  height: 16px;
  accent-color: var(--brand-2);
  cursor: pointer;
}

.actions {
  display: flex;
  gap: 10px;
  margin-top: 20px;
  flex-wrap: wrap;
}

button {
  font: inherit;
  font-weight: 600;
  font-size: 14px;
  padding: 10px 16px;
  border-radius: 8px;
  border: 1px solid transparent;
  cursor: pointer;
}

.btn-primary {
  background: var(--brand-2);
  color: #fff;
}

.btn-primary:hover {
  background: #1d4ed8;
}

.btn-secondary {
  background: #fff;
  color: var(--ink);
  border-color: var(--border);
}

.btn-secondary:hover {
  background: #f8fafc;
}

.preview-wrap {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.preview-stage {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  background:
    linear-gradient(45deg, #eef2f7 25%, transparent 25%) -8px 0 / 16px 16px,
    linear-gradient(-45deg, #eef2f7 25%, transparent 25%) -8px 0 / 16px 16px,
    linear-gradient(45deg, transparent 75%, #eef2f7 75%) -8px 0 / 16px 16px,
    linear-gradient(-45deg, transparent 75%, #eef2f7 75%) -8px 0 / 16px 16px,
    #fff;
  border: 1px solid var(--border);
  border-radius: 10px;
}

/* The ad is exactly 320x100; the iframe matches so preview == output. */
#preview {
  width: 320px;
  height: 100px;
  border: 1px solid var(--border);
  background: #fff;
  display: block;
}

.meta {
  font-size: 12px;
  color: var(--muted);
}

.meta code {
  background: #f1f5f9;
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 12px;
}

.status {
  font-size: 13px;
  min-height: 18px;
  color: var(--brand-2);
}