:root {
  --primary-color: #007aff;
  --primary-light: #5ac8fa;
  --primary-dark: #0056cc;
  --secondary-color: #3a3a3c;
  --text-color: #1d1d1f;
  --background-color: #f5f5f7;
  --section-bg: #ffffff;
  --border-color: rgba(0, 0, 0, 0.1);
  --shadow-color: rgba(0, 0, 0, 0.08);
  --highlight-bg: linear-gradient(135deg, #f2f2f7 0%, #e5e5ea 100%);
  --question-bg: linear-gradient(135deg, #f2f2f7 0%, #e5e5ea 100%);
  --answer-bg: linear-gradient(135deg, #e8f4fd 0%, #d1e9fb 100%);
  --calculation-bg: linear-gradient(135deg, #f8f9fa 0%, #f1f3f4 100%);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Hiragino Sans", Meiryo, sans-serif;
  line-height: 1.6;
  color: var(--text-color);
  background: var(--background-color);
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

header, footer {
  text-align: center;
  margin-bottom: 3rem;
}

header h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: var(--text-color);
  letter-spacing: -0.02em;
}

header p {
  font-size: 1.25rem;
  color: var(--secondary-color);
  font-weight: 400;
  margin-bottom: 2rem;
}

h2 {
  color: var(--text-color);
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  margin-top: 3rem;
  letter-spacing: -0.02em;
}

h3 {
  color: var(--secondary-color);
  font-size: 1.5rem;
  font-weight: 600;
  margin-top: 2.5em;
  margin-bottom: 0.5em;
}

h4 {
  color: var(--secondary-color);
  font-size: 1.25rem;
  font-weight: 600;
  margin-top: 2.5em;
  margin-bottom: 0.5em;
}

section {
  background: var(--section-bg);
  padding: 3rem;
  border-radius: 1.5rem;
  margin-bottom: 2rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  border: 1px solid rgba(0, 0, 0, 0.05);
}

p {
  margin: 1em 0;
  padding: 0;
}

.btn-link {
  display: inline-block;
  margin-top: 2rem;
  padding: 1rem 2rem;
  background: var(--primary-color);
  color: white;
  text-decoration: none;
  border-radius: 1.5rem;
  text-align: center;
  transition: all 0.2s ease;
  font-size: 1.125rem;
  font-weight: 600;
  border: none;
  cursor: pointer;
  box-shadow: 0 1px 3px rgba(0, 122, 255, 0.2);
}

.btn-link:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 122, 255, 0.3);
}

.center {
  text-align: center;
}

.calculation-box {
  background: #343a40;
  color: #a2e0a2;
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin: 0.5em auto;
  max-width: 90%;

  font-family: SF Mono, Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, 'Courier New', monospace;
  font-size: 0.95rem;
  line-height: 1.6;
  white-space: pre-line;
  overflow-x: auto;
  border: 1px solid #555;
}

.highlight {
  background: var(--highlight-bg);
  padding: 2rem;
  margin: 2rem 0;
  border-radius: 1rem;
  font-size: 1.5rem;
  font-weight: 700;
  line-height: 1.7;
  border: 1px solid rgba(0, 0, 0, 0.1);
}

.highlight strong {
  color: var(--primary-color);
  font-weight: 600;
  font-size: 1.1rem;
}
.point {
  padding: 2rem;
  margin: 2rem 0;
  font-size: 1rem;
  line-height: 1.7;
}
.question-box {
  background: var(--question-bg);
  padding: 2rem;
  margin: 2rem 0;
  border-radius: 1rem;
  border: 1px solid rgba(0, 0, 0, 0.1);
}

.answer-box {
  background: linear-gradient(135deg, #e8f4fd 0%, #d1e9fb 100%);
  padding: 1.5rem;
  margin: 1rem 0;
  border-radius: 0.75rem;
  border: 1px solid rgba(0, 122, 255, 0.2);
}

.accordion-content {
  background: var(--answer-bg);
  padding: 1.5rem;
  border-radius: 0.75rem;
  margin-top: 0.5rem;
  border: 1px solid rgba(0, 122, 255, 0.2);
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 2rem 0;
  font-size: 1rem;
  background: white;
  border-radius: 1rem;
  overflow: hidden;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

th, td {
  padding: 1rem;
  text-align: center;
  border-bottom: 1px solid rgba(0, 0, 0, 0.1);
}

th {
  background: var(--highlight-bg);
  font-weight: 600;
  color: var(--text-color);
}

.flow-diagram {
  border: 1px solid rgba(0, 122, 255, 0.2);
  border-radius: 1rem;
  padding: 2rem;
  margin: 2rem 0;
  text-align: left;
  font-size: 1.125rem;
  line-height: 1.8;
  color: var(--text-color);
}

ul, ol {
  padding-left: 2rem;
  margin: 1.5em 0;
}

li {
  margin-bottom: 0.75rem;
  font-size: 1.125rem;
  line-height: 1.8;
  color: var(--secondary-color);
}

p {
  margin: 0.5em 0; /* 余白を調整 */
  font-size: 1.125rem;
  line-height: 1.6; /* 行間を調整 */
  color: var(--secondary-color);
}

.answer {
  font-size: 1.5rem;
  font-weight: bold;
  margin-bottom: 1em;
  color: var(--text-color);
}

strong {
  color: var(--text-color);
  font-weight: 600;
}

.intro-section {
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-light) 100%);
  color: white;
  text-align: center;
  padding: 4rem 3rem;
  border-radius: 2rem;
  margin-bottom: 3rem;
}

.intro-section h2 {
  color: white;
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.intro-section p {
  font-size: 1.375rem;
  color: rgba(255,255,255,0.9);
  margin: 1rem 0;
}

.key-point {
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  padding: 2rem;
  border-radius: 1rem;
  margin: 2rem 0;
  border: 1px solid rgba(0, 122, 255, 0.2);
}

.key-point h4 {
  color: var(--primary-color);
  margin-top: 0;
  margin-bottom: 1rem;
}

.example-box {
  background: var(--question-bg);
  border: 1px solid rgba(0, 0, 0, 0.1);
  border-radius: 1rem;
  padding: 2rem;
  margin-top: 2rem 0;
}

.example-box h4 {
  color: var(--text-color);
  margin-top: 0;
  margin-bottom: 1rem;
}

details {
  margin: 1rem 0;
  background: rgba(0, 0, 0, 0.02); /* ホバー前のグレーの背景色 */
  border: 1px solid rgba(0, 0, 0, 0.1);
  border-radius: 0.5rem;
}

/* アコーディオン（三角アイコン・summaryテキスト）カスタム */
details summary {
  color: var(--text-color);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  padding: 0.75rem 1rem;
  border-radius: 0.5rem;
  transition: all 0.2s ease;
  position: relative;
}

details summary::before {
  display: none;
}

details summary::-webkit-details-marker {
  display: none;
}

details[open] summary {
  background: rgba(0, 0, 0, 0.05); /* 開いた時のsummaryの背景色 */
  border-bottom: 1px solid rgba(0, 0, 0, 0.1); /* 開いた時の区切り線 */
  border-bottom-left-radius: 0;
  border-bottom-right-radius: 0;
}

details[open] summary::before {
  transform: rotate(180deg);
}

details summary:hover {
  background: rgba(0, 0, 0, 0.05); /* ホバー時の背景色 */
  transform: translateY(0); /* ホバー時のアニメーションを削除 */
  box-shadow: none; /* ホバー時の影を削除 */
}

details > *:not(summary) {
  padding: 0.75rem 1rem; /* アコーディオンの中身のパディングを調整 */
}

.explanation-content {
  background: rgba(0, 0, 0, 0.02); /* アコーディオンの背景色 */
  padding: 0.75rem 1rem; /* パディングを調整 */
  border-radius: 0 0 0.5rem 0.5rem; /* 下部の角を丸くする */
  border-top: 1px solid rgba(0, 0, 0, 0.1); /* 上部に区切り線 */
}

.summary-box {
  background: #eef7ff;
  border: 1px solid #a9d7ff;
  border-radius: 1rem;
  padding: 1.2rem;
  margin-bottom: 2rem;
}

.summary-box h4 {
  color: #005a9e;
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1rem; /* フォントサイズを調整 */
}

.summary-box p {
  margin: 0;
  color: #005a9e;
  font-size: 0.9rem; /* フォントサイズを調整 */
}

h2 .fas {
  margin-right: 1rem;
  color: var(--primary-color);
}

/* レスポンシブ対応 */
@media (max-width: 768px) {
  body {
    padding: 1.5rem;
  }
  
  header h1 {
    font-size: 2rem;
  }
  
  header p {
    font-size: 1.125rem;
  }
  
  h2 {
    font-size: 1.75rem;
  }
  
  h3 {
    font-size: 1.375rem;
  }
  
  h4 {
    font-size: 1.125rem;
  }
  
  section {
    padding: 2rem;
  }
  
  .intro-section {
    padding: 3rem 2rem;
  }
  
  .intro-section h2 {
    font-size: 2rem;
  }
  
  .intro-section p {
    font-size: 1.25rem;
  }
  
  .calculation-box {
    padding: 1.5rem;
    font-size: 0.875rem;
  }
  
  .highlight {
    padding: 1.5rem;
  }
  
  table {
    font-size: 0.875rem;
  }
  
  th, td {
    padding: 0.75rem;
  }
  
  .flow-diagram {
    padding: 1.5rem;
    font-size: 1rem;
  }
  
  .key-point, .example-box {
    padding: 1.5rem;
  }
  
  p, li {
    font-size: 1rem;
  }
}

@media (max-width: 480px) {
  body {
    padding: 1rem;
  }
  
  header h1 {
    font-size: 1.75rem;
  }
  
  header p {
    font-size: 1rem;
  }
  
  h2 {
    font-size: 1.5rem;
  }
  
  h3 {
    font-size: 1.25rem;
  }
  
  h4 {
    font-size: 1rem;
  }
  
  section {
    padding: 1rem; /* スマホでsectionのpaddingを1remに設定 */
  }
  
  .intro-section {
    padding: 2rem 1.5rem;
  }
  
  .intro-section h2 {
    font-size: 1.75rem;
  }
  
  .intro-section p {
    font-size: 1.125rem;
  }
  
  .calculation-box {
    padding: 1rem;
    font-size: 0.75rem;
  }
  
  .highlight {
    padding: 1rem;
  }
  
  table {
    font-size: 0.75rem;
  }
  
  th, td {
    padding: 0.5rem;
  }
  
  .flow-diagram {
    padding: 1rem;
    font-size: 0.875rem;
  }
  
  .key-point, .example-box {
    padding: 1rem;
  }
  
  p, li {
    font-size: 0.875rem;
  }
} 

/* --- スマホ専用改行＆字下げ --- */
br-mobile {
  display: none;
}

@media (max-width: 480px) {
  br-mobile {
    display: block;
    height: 0;
    content: "";
  }
  br-mobile + * {
    text-indent: 1.5em;
    display: block;
  }
}

.example {
  font-size: 0.95rem;
  margin-top: 4em;
  margin-bottom: 0.5em;
}

.section-block {
  padding: 2.5em 2em;
  margin: 2.5em 0;
}
.base-block {
  margin-bottom: 2em;
}
.base-block:last-child {
  margin-bottom: 0;
}

.bit-string-example {
  display: flex;
  justify-content: center;
  margin: 20px 0;
}

.bit-box {
  width: 40px;
  height: 40px;
  border: 1px solid #ccc;
  display: flex;
  justify-content: center;
  align-items: center;
  font-weight: bold;
  font-size: 1.2em;
  background-color: #f0f0f0;
}

.bit-box.new-bit {
  background-color: #d4edda; /* 新しく挿入されたビットの背景色 */
  border-color: #28a745;
}

.arrow {
  text-align: center;
  font-size: 0.9em;
  margin: 10px 0;
}


.shifted .bit-box:first-child {
  border-left: 2px solid #007bff;
}

.shifted .bit-box:last-child {
  border-right: 2px solid #dc3545;
}

.shifted .bit-box:not(.new-bit) {
  background-color: #e9ecef;
}

.shifted .bit-box:not(.new-bit):nth-child(odd) {
  background-color: #e2e6ea;
}

.shifted .bit-box:not(.new-bit):nth-child(even) {
  background-color: #dae0e5;
}

.question-item {
  margin-bottom: 2rem;
}