:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #15181d;
  --muted: #5f6b7a;
  --border: #dde2e8;
  --accent: #2f6fed;
  --accent-text: #ffffff;
  --err: #c53b3b;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1216;
    --surface: #171b21;
    --text: #e6e9ee;
    --muted: #97a3b3;
    --border: #2a313a;
    --accent: #6b98ff;
    --accent-text: #0b0e12;
    --err: #ff7a7a;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.55 -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo", "Malgun Gothic", "Noto Sans KR", sans-serif;
}

.box {
  width: 100%;
  max-width: 380px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

h1 { font-size: 18px; margin: 0 0 6px; }
.hint { color: var(--muted); font-size: 14px; margin: 0 0 14px; }

form { display: flex; flex-direction: column; gap: 10px; }

input {
  width: 100%;
  font: 16px ui-monospace, SFMono-Regular, Consolas, monospace;
  letter-spacing: 1px;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
}

button {
  border: 0;
  border-radius: 10px;
  padding: 11px 14px;
  font: inherit;
  font-weight: 650;
  background: var(--accent);
  color: var(--accent-text);
  cursor: pointer;
}

.msg { min-height: 1.5em; margin: 12px 0 0; font-size: 14px; color: var(--err); }