* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Oxygen", "Ubuntu", "Cantarell", "Fira Sans",
    "Droid Sans", "Helvetica Neue", sans-serif;
  line-height: 1.6;
  color: #333;
  background-color: #f9f9f9;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header {
  padding: 2rem 1rem;
  border-bottom: 1px solid #e0e0e0;
  background-color: white;
  text-align: center;
}

header h1 {
  font-size: 1.875rem;
  font-weight: bold;
  color: #1a1a1a;
}

.header-description {
  margin-top: 0.5rem;
  font-size: 0.875rem;
  color: #666;
  font-weight: normal;
}

main {
  flex: 1;
  max-width: 48rem;
  width: 100%;
  margin: 0 auto;
  padding: 2rem 1rem;
}

.hint-section {
  margin-bottom: 3rem;
  background-color: white;
  padding: 1.5rem;
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.hint-section h2 {
  font-size: 1.5rem;
  font-weight: 600;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid #e0e0e0;
  margin-bottom: 1rem;
  color: #1a1a1a;
}

/* マスクテキスト */
.masked-text {
  background-color: #222222;
  color: inherit;
  user-select: text;
  cursor: text;
  transition: background-color 0.2s;
}

.masked-text:hover {
  background-color: #cccccc;
}

.masked-revealed {
  background-color: #cccccc;
}

.main-lines {
  padding-left: 1rem;
  margin-top: 1rem;
}

.main-lines p {
  margin-bottom: 0.75rem;
}

.subsections {
  margin-top: 1.5rem;
}

.subsection {
  padding-left: 1rem;
  border-left: 2px solid #e0e0e0;
  margin-bottom: 2rem;
}

.subsection h3 {
  font-size: 1.25rem;
  font-weight: 500;
  color: #1a1a1a;
  margin-bottom: 0.75rem;
}

.subsection-lines {
  padding-left: 1rem;
}

.subsection-lines p {
  margin-bottom: 0.75rem;
}

.hint-button {
  background-color: #ffffff;
  color: #1a1a1a;
  border: 1px solid #d0d0d0;
  padding: 0.5rem 1rem;
  border-radius: 6px;
  cursor: pointer;
  font-size: 0.875rem;
  font-weight: 500;
  margin-top: 0.5rem;
  transition: all 0.2s;
}

.hint-button:hover {
  background-color: #f5f5f5;
  border-color: #b0b0b0;
}

.hint-button:active {
  transform: scale(0.98);
}

footer {
  padding: 1.5rem 1rem;
  border-top: 1px solid #e0e0e0;
  background-color: white;
  text-align: center;
  font-size: 0.875rem;
  color: #666;
}

@media (max-width: 640px) {
  header h1 {
    font-size: 1.5rem;
  }

  .hint-section h2 {
    font-size: 1.25rem;
  }

  .subsection h3 {
    font-size: 1.125rem;
  }
}