* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: #14171c;
  color: #e8eaed;
  min-height: 100vh;
}

header {
  padding: 24px 16px 8px;
  text-align: center;
}

header h1 {
  margin: 0;
  font-size: 1.6rem;
}

.subtitle {
  margin: 4px 0 0;
  color: #9aa0a6;
  font-size: 0.9rem;
}

main {
  max-width: 520px;
  margin: 0 auto;
  padding: 16px;
}

.tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
}

.tab-btn {
  flex: 1;
  padding: 10px;
  background: #22262e;
  border: 1px solid #33383f;
  border-radius: 8px;
  color: #e8eaed;
  font-size: 0.95rem;
  cursor: pointer;
}

.tab-btn.active {
  background: #3b82f6;
  border-color: #3b82f6;
  color: #fff;
}

.tab-panel {
  display: none;
  margin-bottom: 16px;
}

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

.subtabs {
  display: flex;
  gap: 6px;
  margin-bottom: 12px;
}

.subtab-btn {
  flex: 1;
  padding: 7px;
  background: transparent;
  border: 1px solid #33383f;
  border-radius: 6px;
  color: #9aa0a6;
  font-size: 0.85rem;
  cursor: pointer;
}

.subtab-btn.active {
  background: #1c1f26;
  border-color: #3b82f6;
  color: #e8eaed;
}

.subtab-panel {
  display: none;
}

.subtab-panel.active {
  display: block;
}

.subtab-panel label {
  margin-top: 10px;
}

.subtab-panel label:first-child {
  margin-top: 0;
}

select {
  width: 100%;
  padding: 10px;
  background: #1c1f26;
  border: 1px solid #33383f;
  border-radius: 8px;
  color: #e8eaed;
  font-size: 1rem;
}

label {
  display: block;
  font-size: 0.85rem;
  color: #9aa0a6;
  margin-bottom: 6px;
}

textarea,
input[type="text"],
input[type="number"] {
  width: 100%;
  padding: 10px;
  background: #1c1f26;
  border: 1px solid #33383f;
  border-radius: 8px;
  color: #e8eaed;
  font-size: 1rem;
}

input[type="file"] {
  width: 100%;
  color: #e8eaed;
  margin-bottom: 8px;
}

button {
  padding: 10px 16px;
  border-radius: 8px;
  border: none;
  background: #3b82f6;
  color: #fff;
  font-size: 0.95rem;
  cursor: pointer;
}

button:disabled {
  background: #33383f;
  color: #6b7076;
  cursor: not-allowed;
}

#decode-btn {
  width: 100%;
}

.controls {
  background: #1c1f26;
  border: 1px solid #33383f;
  border-radius: 10px;
  padding: 14px;
  margin-bottom: 16px;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 8px;
  color: #e8eaed;
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.checkbox-row input {
  width: auto;
}

.helper-text {
  font-size: 0.78rem;
  color: #9aa0a6;
  margin: 0 0 14px;
}

.dims {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.dims label {
  margin-bottom: 0;
}

.preview {
  margin-bottom: 16px;
}

#preview-wrap {
  aspect-ratio: 1 / 1;
  max-width: 320px;
  margin: 0 auto;
  background: #1c1f26;
  border: 1px solid #33383f;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

#preview-img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  image-rendering: pixelated;
}

#preview-placeholder {
  color: #6b7076;
  font-size: 0.85rem;
  margin: 0;
  padding: 16px;
  text-align: center;
}

.status {
  font-size: 0.85rem;
  margin: 8px 0 0;
  text-align: center;
}

.status.error {
  color: #f87171;
}

.status.success {
  color: #4ade80;
}

#download-btn {
  width: 100%;
  padding: 14px;
  font-size: 1.05rem;
}

@media (max-width: 420px) {
  .dims {
    grid-template-columns: 1fr;
  }
}