:root {
  --bg: #f4f5f7;
  --card-bg: #ffffff;
  --text: #1f2430;
  --muted: #5b6472;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --border: #dde1e7;
  --error: #b3261e;
  --warn: #92400e;
  --radius: 10px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.5;
}

.card {
  width: 100%;
  max-width: 560px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 8px 24px rgba(0, 0, 0, 0.04);
}

h1 {
  font-size: 1.4rem;
  margin: 0 0 16px;
}

p {
  color: var(--muted);
  margin: 0 0 16px;
}

textarea {
  width: 100%;
  min-height: 220px;
  resize: vertical;
  padding: 12px;
  font-family: inherit;
  font-size: 0.95rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fbfbfc;
  color: var(--text);
}

textarea:focus,
input[type="text"]:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

button {
  margin-top: 12px;
  padding: 10px 18px;
  font-size: 0.95rem;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  border: none;
  border-radius: 8px;
  cursor: pointer;
}

button:hover {
  background: var(--accent-hover);
}

.link-box {
  display: flex;
  gap: 8px;
  margin-bottom: 8px;
  flex-wrap: wrap;
}

.link-box input[type="text"] {
  flex: 1 1 220px;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
  background: #fbfbfc;
  color: var(--text);
}

.link-box button {
  margin-top: 0;
}

.info-list {
  padding-left: 20px;
  color: var(--muted);
}

.info-list li {
  margin-bottom: 6px;
}

.secret-box {
  white-space: pre-wrap;
  word-break: break-word;
  background: #fbfbfc;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9rem;
  color: var(--text);
}

.error {
  color: var(--error);
  font-weight: 600;
}

.warn {
  color: var(--warn);
  font-weight: 600;
}

.hint {
  font-size: 0.85rem;
}

.feedback {
  min-height: 1.2em;
  font-size: 0.85rem;
  color: var(--accent);
  font-weight: 600;
}

a {
  color: var(--accent);
}

@media (max-width: 480px) {
  .card {
    padding: 20px;
  }
}