* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  background: #171944;
  color: #fff;
  font-family: Arial, "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  animation: fadeIn .6s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0
  }
}

header {
  width: 100%;
  max-width: 480px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 16px;
}

header img {
  display: block;
  height: 40px;
  border-radius: 8px;
}

.back {
  padding: 8px 18px;
  border: 2px solid #fff;
  border-radius: 999px;
  color: #fff;
  text-decoration: none;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .12em;
  transition: background .3s, color .3s;
}

.back:hover {
  background: #fff;
  color: #171944;
}

canvas {
  display: block;
  border-radius: 16px;
  touch-action: manipulation;
  cursor: pointer;
}

.hint {
  margin: 12px 0 24px;
  font-size: 12px;
  opacity: .65;
  letter-spacing: .1em;
}