:root {
  --bg: #111417;
  --panel: #1a1f24;
  --panel-2: #20262c;
  --line: #313a44;
  --text: #e7edf2;
  --muted: #aab5bf;
  --accent: #6ea39d;
  --accent-2: #d48e94;
  --button: #29313a;
  --button-hover: #34404c;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
  --radius: 14px;
  --radius-sm: 10px;
  --font: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
}

body {
  min-height: 100vh;
}

button,
input,
label {
  font: inherit;
}

.app-shell {
  max-width: 1600px;
  margin: 0 auto;
  padding: 24px;
}

.app-header {
  margin-bottom: 20px;
}

.app-header h1 {
  margin: 0 0 8px;
  font-size: clamp(1.75rem, 2vw, 2.4rem);
}

.app-header p {
  margin: 0;
  color: var(--muted);
  line-height: 1.45;
}

.layout {
  display: grid;
  grid-template-columns: 370px minmax(0, 1fr);
  gap: 20px;
  align-items: start;
}

.controls-panel,
.preview-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.controls-panel {
  padding: 18px;
}

.panel-section + .panel-section {
  margin-top: 20px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.panel-section h2 {
  margin: 0 0 12px;
  font-size: 1.05rem;
}

.file-label,
button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 40px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--line);
  background: var(--button);
  color: var(--text);
  padding: 0 14px;
  cursor: pointer;
  transition: 0.15s ease background, 0.15s ease border-color, 0.15s ease transform;
}

button:hover,
.file-label:hover {
  background: var(--button-hover);
}

button:active,
.file-label:active {
  transform: translateY(1px);
}

button.secondary {
  background: transparent;
}

#fileInput {
  display: none;
}

.action-row,
.preset-grid {
  display: grid;
  gap: 10px;
}

.action-row {
  grid-template-columns: 1fr 1fr;
  margin-top: 12px;
}

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

.meta {
  margin-top: 14px;
  color: var(--muted);
  font-size: 0.92rem;
  line-height: 1.45;
}

.meta div + div {
  margin-top: 4px;
}

.control + .control {
  margin-top: 14px;
}

.control label {
  display: block;
  margin-bottom: 8px;
  font-weight: 600;
}

.control-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 10px;
  align-items: center;
}

.color-row {
  grid-template-columns: 56px auto;
  justify-content: start;
}

.value-pill {
  min-width: 72px;
  text-align: right;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--panel-2);
  color: var(--muted);
  border: 1px solid var(--line);
  font-variant-numeric: tabular-nums;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
}

input[type="color"] {
  width: 56px;
  height: 40px;
  padding: 0;
  border: 1px solid var(--line);
  background: transparent;
  border-radius: 10px;
  cursor: pointer;
}

.preview-panel {
  min-width: 0;
  position: sticky;
  top: 16px;
  align-self: start;
}

.preview-card {
  padding: 14px;
}

.preview-stage {
  position: relative;
  width: 100%;
  min-height: 420px;
  display: grid;
  place-items: center;
  background:
    linear-gradient(45deg, rgba(255,255,255,0.03) 25%, transparent 25%),
    linear-gradient(-45deg, rgba(255,255,255,0.03) 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, rgba(255,255,255,0.03) 75%),
    linear-gradient(-45deg, transparent 75%, rgba(255,255,255,0.03) 75%);
  background-size: 24px 24px;
  background-position: 0 0, 0 12px, 12px -12px, -12px 0;
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid var(--line);
}

.preview-stage canvas {
  display: block;
  max-width: 100%;
  max-height: calc(100vh - 100px);
  width: auto;
  height: auto;
}

.preview-overlay {
  position: absolute;
  inset: 0;
  margin: auto;
  pointer-events: none;
}

.split-line {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 2px;
  background: rgba(255, 255, 255, 0.88);
  box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.18);
  pointer-events: none;
}

.preview-note {
  margin-top: 12px;
  color: var(--muted);
  font-size: 0.95rem;
}

@media (max-width: 1120px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .preview-panel {
    position: static;
  }
}

@media (max-width: 640px) {
  .app-shell {
    padding: 16px;
  }

  .action-row {
    grid-template-columns: 1fr;
  }
}