html, body {
  margin: 0;
  height: 100%;
  background: #1a1414;
  color: #f3ece6;
  font-family: "Noto Sans JP", "Hiragino Sans", "Yu Gothic", "Meiryo", sans-serif;
  overflow: hidden;
}
canvas { display: block; }
body.preview canvas { cursor: crosshair; }

#title {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  box-sizing: border-box;
  background: radial-gradient(ellipse at 50% 120%, #7a2410 0%, #2a1612 55%, #140f0e 100%);
  z-index: 10;
  overflow-y: auto;
}
#title[hidden] { display: none; }

.card {
  max-width: 460px;
  width: 100%;
  text-align: center;
}
h1 {
  margin: 0 0 8px;
  font-size: clamp(56px, 16vw, 96px);
  letter-spacing: 0.04em;
  color: #ff5a1f;
  text-shadow: 0 0 24px rgba(255, 120, 30, 0.55);
}
.lead { margin: 0 0 28px; line-height: 1.7; }

button {
  font: inherit;
  border: 0;
  border-radius: 12px;
  cursor: pointer;
}
#btn-start {
  width: 100%;
  padding: 20px;
  font-size: 28px;
  font-weight: bold;
  color: #fff;
  background: #d8341a;
  box-shadow: 0 6px 0 #8a1d0c;
}
#btn-start:disabled {
  background: #5a4440;
  box-shadow: 0 6px 0 #33282a;
  color: #b9a9a3;
  cursor: not-allowed;
}
.sub {
  margin-top: 8px;
  padding: 12px 20px;
  font-size: 17px;
  color: #f3ece6;
  background: #3b2e2b;
}
.status {
  min-height: 1.5em;
  margin: 16px 0;
  font-size: 15px;
  line-height: 1.6;
  color: #ffd2a8;
}
.status.error { color: #ff9a8a; }
.howto {
  margin: 28px 0 0;
  padding: 0;
  list-style: none;
  text-align: left;
  font-size: 14px;
  line-height: 1.7;
  color: #cbbdb6;
}
.howto li { margin-bottom: 6px; }

#btn-back {
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 5;
  padding: 8px 14px;
  font-size: 14px;
  color: #f3ece6;
  background: rgba(40, 30, 28, 0.8);
}
#btn-back[hidden] { display: none; }