:root {
  --bg: #ffffff;
  --card: #ffffff;
  --ink: #16181d;
  --muted: #6b7280;
  --line: #e3e6ea;
  --line-strong: #cfd4da;
  --accent: #2563eb;
  --accent-ink: #ffffff;
  --ok: #157347;
  --err: #b42318;
  --radius: 10px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1115;
    --card: #161a20;
    --ink: #e8eaed;
    --muted: #9aa1ab;
    --line: #262b33;
    --line-strong: #333a44;
    --accent: #4f8cff;
    --accent-ink: #0f1115;
    --ok: #4ec98a;
    --err: #ff6b60;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.wrap {
  max-width: 560px;
  margin: 0 auto;
  padding: 48px 20px 40px;
}

.head { text-align: center; margin-bottom: 24px; }
.head h1 {
  margin: 0;
  font-size: 30px;
  font-weight: 650;
  letter-spacing: -0.02em;
}
.sub { margin: 6px 0 0; color: var(--muted); }

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

.drop {
  border: 1.5px dashed var(--line-strong);
  border-radius: var(--radius);
  padding: 32px 20px;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}
.drop:hover, .drop:focus, .drop.over {
  border-color: var(--accent);
  outline: none;
}
.drop-title { margin: 0 0 4px; font-weight: 600; }
.drop-hint { margin: 0 0 14px; color: var(--muted); font-size: 14px; }
.chosen {
  margin: 14px 0 0;
  font-size: 14px;
  font-weight: 600;
  word-break: break-all;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.9em;
  padding: 1px 5px;
  background: var(--line);
  border-radius: 5px;
}

.btn {
  display: inline-block;
  border: 1px solid transparent;
  border-radius: 8px;
  padding: 10px 18px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  text-align: center;
}
.btn.primary {
  background: var(--accent);
  color: var(--accent-ink);
  width: 100%;
  margin-top: 18px;
}
.btn.primary:disabled { opacity: 0.45; cursor: not-allowed; }
.btn.ghost {
  background: transparent;
  color: var(--ink);
  border-color: var(--line-strong);
}

.preview {
  margin: 18px 0 0;
}
.preview-frame {
  position: relative;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: repeating-conic-gradient(var(--line) 0% 25%, transparent 0% 50%) 50% / 20px 20px;
  aspect-ratio: 16 / 9;
  display: flex;
  align-items: center;
  justify-content: center;
}
.preview-frame img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}
.preview-spinner {
  position: absolute;
  width: 26px;
  height: 26px;
  border: 3px solid rgba(127, 127, 127, 0.35);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
.preview-note {
  margin: 8px 0 0;
  font-size: 12px;
  color: var(--muted);
  text-align: center;
}

.opts { margin-top: 18px; }
.opts summary {
  cursor: pointer;
  color: var(--muted);
  font-size: 14px;
  font-weight: 600;
  padding: 4px 0;
}
.opts-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 12px;
}
.opts-grid label {
  display: flex;
  flex-direction: column;
  gap: 5px;
  font-size: 13px;
  color: var(--muted);
  font-weight: 600;
}
.opts-grid select {
  font: inherit;
  font-size: 14px;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--line-strong);
  border-radius: 7px;
  padding: 7px 8px;
}

.progress { margin-top: 18px; }
.bar {
  height: 8px;
  background: var(--line);
  border-radius: 999px;
  overflow: hidden;
}
.bar span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--accent);
  transition: width 0.3s ease;
}
.status { margin: 10px 0 0; font-size: 14px; color: var(--muted); text-align: center; }

.result { margin-top: 18px; text-align: center; }
.result .btn.ghost { width: 100%; margin-top: 10px; }
.warn {
  list-style: none;
  margin: 14px 0 0;
  padding: 0;
  text-align: left;
  font-size: 13px;
  color: var(--muted);
}
.warn li { padding: 4px 0; border-top: 1px solid var(--line); }

.error {
  margin: 16px 0 0;
  padding: 12px 14px;
  border: 1px solid var(--err);
  border-radius: 8px;
  color: var(--err);
  font-size: 14px;
  white-space: pre-wrap;
}

.help { margin-top: 22px; }
.help summary { cursor: pointer; font-size: 14px; font-weight: 600; }
.help ol { margin: 12px 0; padding-left: 20px; }
.help li { margin: 4px 0; }
.muted { color: var(--muted); font-size: 13px; }

.seo { margin-top: 34px; }
.seo h2 {
  margin: 0 0 10px;
  font-size: 19px;
  font-weight: 650;
  letter-spacing: -0.01em;
}
.seo h3 {
  margin: 18px 0 8px;
  font-size: 15px;
  font-weight: 650;
}
.seo p { margin: 0 0 10px; color: var(--muted); font-size: 14px; }
.seo a { color: var(--accent); }

.features {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 16px;
}
.features li {
  position: relative;
  padding-left: 20px;
  font-size: 14px;
  color: var(--muted);
}
.features li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--ok);
  font-weight: 700;
}

.faq {
  border-top: 1px solid var(--line);
  padding: 12px 0;
}
.faq summary {
  cursor: pointer;
  font-size: 14px;
  font-weight: 600;
}
.faq p { margin: 10px 0 0; }

.foot {
  margin-top: 28px;
  text-align: center;
  color: var(--muted);
  font-size: 13px;
}

@media (max-width: 460px) {
  .features { grid-template-columns: 1fr; }
}

@media (max-width: 460px) {
  .opts-grid { grid-template-columns: 1fr; }
}