/* =========================================================
   Concept Page — Page-specific Styles
   ※ ヒーロー（.page-hero*）と MV 画像（.page-mv*）の共通スタイルは
     style.css に定義済み。本ファイルはこのページ固有のセクションスタイル。
   ========================================================= */

.concept-page-section {
  padding: 4rem 0;
}

@media (min-width: 768px) {
  .concept-page-section {
    padding: 6rem 0;
  }
}

.concept-page-intro-section {
  padding-top: 1.5rem;
}

@media (min-width: 768px) {
  .concept-page-intro-section {
    padding-top: 6rem;
  }
}

.concept-page-intro {
  text-align: center;
  max-width: 720px;
  margin: 0 auto;
}

.concept-page-intro__eyebrow {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.875rem;
  margin-bottom: 2.25rem;
}

@media (min-width: 768px) {
  .concept-page-intro__eyebrow {
    gap: 1.25rem;
    margin-bottom: 3rem;
  }
}

.concept-page-intro__eyebrow-rule {
  display: block;
  width: 2.25rem;
  height: 1px;
  background-color: var(--color--ink--light);
  opacity: 0.45;
}

@media (min-width: 768px) {
  .concept-page-intro__eyebrow-rule {
    width: 3.5rem;
  }
}

.concept-page-intro__eyebrow-label {
  font-size: 0.8125rem;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--color--ink--light);
  font-style: italic;
}

@media (min-width: 768px) {
  .concept-page-intro__eyebrow-label {
    font-size: 0.9375rem;
  }
}

.concept-page-intro__keywords {
  display: flex;
  align-items: baseline;
  justify-content: center;
  gap: 1.25rem;
  margin-bottom: 2rem;
}

@media (min-width: 768px) {
  .concept-page-intro__keywords {
    gap: 2.5rem;
    margin-bottom: 2.75rem;
  }
}

.concept-page-intro__keyword {
  font-size: 2.125rem;
  letter-spacing: 0.18em;
  font-weight: 400;
  color: var(--color--ink);
  line-height: 1;
}

@media (min-width: 768px) {
  .concept-page-intro__keyword {
    font-size: 3.25rem;
    letter-spacing: 0.22em;
  }
}

.concept-page-intro__keyword-mark {
  font-size: 1.5rem;
  font-style: italic;
  font-weight: 300;
  color: var(--color--ink--light);
  line-height: 1;
  transform: translateY(-0.35em);
}

@media (min-width: 768px) {
  .concept-page-intro__keyword-mark {
    font-size: 2.25rem;
  }
}

.concept-page-intro__title {
  font-size: 1.1875rem;
  margin: 0 auto;
  line-height: 2;
  text-align: center;
  font-weight: 500;
  color: var(--color--ink);
  max-width: 24em;
}

@media (min-width: 768px) {
  .concept-page-intro__title {
    font-size: 1.625rem;
    line-height: 2.1;
    max-width: 28em;
  }
}

.concept-page-intro__title-accent {
  display: inline-block;
  font-size: 1.25em;
  letter-spacing: 0.04em;
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  padding: 0 0.05em;
}

.concept-page-intro__divider {
  display: block;
  width: 1px;
  height: 3rem;
  background-color: var(--color--ink--light);
  opacity: 0.3;
  margin: 2.5rem auto;
}

@media (min-width: 768px) {
  .concept-page-intro__divider {
    height: 4rem;
    margin: 3.25rem auto;
  }
}

.concept-page-intro__text {
  font-size: 1rem;
  line-height: 2;
  width: fit-content;
  max-width: 100%;
  margin-inline: auto;
  text-align: left;
}

@media (min-width: 768px) {
  .concept-page-intro__text {
    font-size: 1.0625rem;
    line-height: 2.1;
  }
}

/* ----- Pillars: Diagram (ベン図 SVG) ----- */
.concept-page-pillars__diagram {
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 0 auto 3rem;
  max-width: 460px;
}

@media (min-width: 768px) {
  .concept-page-pillars__diagram {
    margin: 0 auto 4.5rem;
  }
}

.concept-page-pillars__diagram-svg {
  width: 100%;
  height: auto;
}

/* ----- Pillars: 3つのカード（grid） ----- */
.concept-page-pillars {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2.5rem;
}

@media (min-width: 768px) {
  .concept-page-pillars {
    grid-template-columns: repeat(3, 1fr);
    gap: 2.5rem;
  }
}

/* ----- Pillars: 各カード本体（罫線フレーム + 白背景） ----- */
.concept-page-pillar {
  display: flex;
  flex-direction: column;
  background: #ffffff;
  border: 1px solid rgba(0, 0, 0, 0.18);
  padding: 1.75rem 1.5rem;
}

@media (min-width: 768px) {
  .concept-page-pillar {
    padding: 2rem 1.75rem;
  }
}

/* ----- Pillars: ヘッダー ( 番号 + Variable / 変数 ) ----- */
/* 見出しはカード内中央寄せ。番号は左に絶対配置（中央配置に影響しない） */
.concept-page-pillar__header {
  position: relative;
  display: block;
  text-align: center;
  min-height: 3.5rem;
  margin-bottom: 1.5rem;
}

@media (min-width: 768px) {
  .concept-page-pillar__header {
    min-height: 4.25rem;
  }
}

.concept-page-pillar__num-chip {
  position: absolute;
  top: 40%;
  left: 0;
  transform: translateY(-50%);
  line-height: 1;
}

.concept-page-pillar__num {
  font-family: var(--font--display);
  font-size: 3.25rem;
  font-style: italic;
  font-weight: 500;
  line-height: 1;
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  opacity: 0.45;
}

@media (min-width: 768px) {
  .concept-page-pillar__num {
    font-size: 4rem;
  }
}

.concept-page-pillar__title-block {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
}

.concept-page-pillar__accent {
  font-size: 0.875rem;
  font-style: italic;
  font-weight: 400;
  color: var(--color--ink--light);
  letter-spacing: 0.18em;
  background: none;
  -webkit-text-fill-color: currentColor;
  -webkit-background-clip: border-box;
  background-clip: border-box;
}

@media (min-width: 768px) {
  .concept-page-pillar__accent {
    font-size: 0.9375rem;
  }
}

.concept-page-pillar__title {
  font-size: 1.5rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  margin: 0;
  line-height: 1.3;
}

@media (min-width: 768px) {
  .concept-page-pillar__title {
    font-size: 1.75rem;
  }
}

/* ----- Pillars: 引用ブロック ----- */
.concept-page-pillar__quote {
  font-size: 1.0625rem;
  font-weight: 500;
  line-height: 1.85;
  letter-spacing: 0.03em;
  margin: 0 0 1.75rem;
  color: var(--color--ink);
}

@media (min-width: 768px) {
  .concept-page-pillar__quote {
    font-size: 1.125rem;
    line-height: 1.9;
    margin-bottom: 2rem;
  }
}

/* ----- Pillars: 箇条書き ----- */
.concept-page-pillar__list {
  list-style: none;
  padding: 0;
  margin: 0 0 1.5rem;
  font-size: 0.9375rem;
  line-height: 2;
}

.concept-page-pillar__list li {
  position: relative;
  padding-left: 1em;
  margin: 0;
}

.concept-page-pillar__list li::before {
  content: '·';
  position: absolute;
  left: 0;
  color: var(--color--ink--light);
}

/* ----- Pillars: 詳細説明文 ----- */
.concept-page-pillar__desc {
  font-size: 0.9375rem;
  line-height: 1.95;
  color: var(--color--ink--light);
  margin: 0;
}

.concept-page-identity__grid {
  display: flex;
  flex-direction: column;
  gap: 3rem;
  align-items: center;
}

.concept-page-identity-section {
  padding-bottom: var(--space-section-bottom);
  background-color: #ffffff;
}

@media (min-width: 768px) {
  .concept-page-identity__grid {
    gap: 4rem;
  }
}

.concept-page-identity__logo-box {
  max-width: 400px;
  margin: 0 auto;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
}

@media (min-width: 768px) {
  .concept-page-identity__logo-box {
    gap: 1.5rem;
  }
}

.concept-page-identity__logo-caption {
  font-size: 0.8125rem;
  font-style: italic;
  color: var(--color--ink--light);
  letter-spacing: 0.2em;
}

@media (min-width: 768px) {
  .concept-page-identity__logo-caption {
    font-size: 0.9375rem;
    letter-spacing: 0.22em;
  }
}

.concept-page-identity__logo-img {
  width: 100%;
  height: auto;
  object-fit: contain;
}

.concept-page-identity__features {
  display: flex;
  flex-direction: column;
  gap: 0;
  width: 100%;
}

@media (min-width: 768px) {
  .concept-page-identity__features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0 4rem;
  }
}

.concept-page-identity__feature {
  background-color: transparent;
  padding: 2.25rem 0;
  border: none;
  border-top: 1px solid rgba(0, 0, 0, 0.08);
  border-radius: 0;
  position: relative;
  box-shadow: none;
}

.concept-page-identity__feature:last-child {
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
}

@media (min-width: 768px) {
  .concept-page-identity__feature:nth-last-child(2) {
    border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  }
}

.concept-page-identity__feature::before {
  display: none;
}

.concept-page-identity__feature-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

.concept-page-identity__feature-icon {
  font-size: 2.5rem;
  font-weight: 800;
  font-family: var(--font--display);
  font-style: italic;
  line-height: 1;
  width: 3.75rem;
  padding-right: 0.25em;
  text-align: right;
  flex-shrink: 0;
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  color: transparent;
}

.concept-page-identity__feature-title {
  font-size: 1.25rem;
  margin: 0;
  letter-spacing: 0.05em;
  font-weight: bold;
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  color: transparent;
}

.concept-page-identity__feature-desc {
  font-size: 0.9375rem;
  line-height: 1.9;
  color: var(--color--ink--light);
  margin-bottom: 0;
}

@media (min-width: 768px) {
  .concept-page-identity__feature-desc {
    padding-left: 4.5rem;
  }
}

/* Desktop Radial Bento Grid Layout */
@media (min-width: 1024px) {
  .concept-page-identity__grid {
    display: grid;
    grid-template-columns: 1fr minmax(280px, 400px) 1fr;
    grid-template-rows: auto auto;
    gap: 6rem 4rem;
    align-items: center;
  }

  .concept-page-identity__image {
    grid-column: 2 / 3;
    grid-row: 1 / 3;
    display: flex;
    justify-content: center;
    align-items: center;
  }

  .concept-page-identity__features {
    display: contents; /* Unbox features wrapper so children join the main grid */
  }

  /* Positioning the 4 features */
  .concept-page-identity__feature:nth-child(1) { grid-column: 1 / 2; grid-row: 1 / 2; }
  .concept-page-identity__feature:nth-child(2) { grid-column: 3 / 4; grid-row: 1 / 2; }
  .concept-page-identity__feature:nth-child(3) { grid-column: 1 / 2; grid-row: 2 / 3; }
  .concept-page-identity__feature:nth-child(4) { grid-column: 3 / 4; grid-row: 2 / 3; }
}

/* =========================================================
   Promise: 手紙型レイアウト
   左 .promise-letter__body : 透かしの本マーク + 書簡（リード/本文/署名）
   右 .promise-letter__index: 「私たちが提供する価値」を 01〜07 の連番で
   ========================================================= */
.promise-letter {
  position: relative;
  background-color: #fcfbf8;
  border-top: 1px solid rgba(27, 110, 188, 0.18);
  border-bottom: 1px solid rgba(27, 110, 188, 0.08);
  padding: 2.5rem 1.5rem;
}

.promise-letter__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2.75rem;
  max-width: 1080px;
  margin: 0 auto;
}

.promise-letter__body {
  position: relative;
}

.promise-letter__bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0.06;
  overflow: hidden;
}

.promise-letter__book {
  width: 78%;
  max-width: 280px;
  height: auto;
  transform: rotate(-4deg);
}

.promise-letter__body > *:not(.promise-letter__bg) {
  position: relative;
  z-index: 1;
}

.promise-letter__kicker {
  font-size: 0.6875rem;
  letter-spacing: 0.3em;
  color: var(--color--accent);
  text-transform: uppercase;
  margin-bottom: 1.25rem;
  display: block;
}

.promise-letter__title {
  font-size: 1.5rem;
  line-height: 1.55;
  letter-spacing: 0.08em;
  margin-bottom: 1.75rem;
  font-weight: 500;
}

.promise-letter__text {
  font-size: 1rem;
  line-height: 2;
  letter-spacing: 0.05em;
  color: var(--color--ink);
}

.promise-letter__text p {
  margin-bottom: 1.25rem;
}

.promise-letter__text p:last-child {
  margin-bottom: 0;
}

.promise-letter__lead {
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  font-weight: 500;
}

.promise-letter__sign {
  display: block;
  margin-top: 1.75rem;
  font-size: 0.875rem;
  letter-spacing: 0.2em;
  color: var(--color--ink--light);
}

.promise-letter__index-eyebrow {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.375rem;
  padding-bottom: 0.875rem;
  border-bottom: 1px solid rgba(0, 0, 0, 0.12);
  margin-bottom: 1.25rem;
}

.promise-letter__index-eyebrow-en {
  font-size: 0.6875rem;
  letter-spacing: 0.3em;
  color: var(--color--ink--light);
  text-transform: uppercase;
}

.promise-letter__index-eyebrow-ja {
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  color: var(--color--ink);
  font-weight: 500;
}

.promise-letter__list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.promise-letter__item {
  display: grid;
  grid-template-columns: 2.25rem 1fr;
  align-items: baseline;
  gap: 0.875rem;
  padding: 0.875rem 0;
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
}

.promise-letter__item:last-child {
  border-bottom: none;
}

.promise-letter__num {
  font-size: 1rem;
  letter-spacing: 0.08em;
  color: var(--color--accent);
  font-weight: 500;
}

.promise-letter__item-text {
  font-size: 0.9375rem;
  line-height: 1.7;
  letter-spacing: 0.04em;
  color: var(--color--ink);
}

@media (min-width: 768px) {
  .promise-letter {
    padding: 4.5rem 4rem;
  }
  .promise-letter__grid {
    grid-template-columns: minmax(0, 5fr) minmax(0, 6fr);
    gap: 5rem;
  }
  .promise-letter__title {
    font-size: 2rem;
    margin-bottom: 2.25rem;
  }
  .promise-letter__text {
    font-size: 1.0625rem;
  }
  .promise-letter__index-eyebrow {
    margin-bottom: 1.5rem;
  }
  .promise-letter__item {
    grid-template-columns: 2.75rem 1fr;
    padding: 1.125rem 0;
    gap: 1.25rem;
  }
  .promise-letter__num {
    font-size: 1.125rem;
  }
  .promise-letter__item-text {
    font-size: 1rem;
  }
}

/* =========================================================
   Story Section — Memoir Chapter Opener (.story-memoir)
   Concept ページ「Story / なぜ「変数と文学」なのか」セクションの本体。
   章番号 + 章タイトル + ドロップキャップ + 引用 + 結語 で構成する書籍風レイアウト。
   ========================================================= */
.story-memoir__chapter {
  background-color: #fdfbf6;
  padding: 2.5rem 1.5rem;
  position: relative;
}

.story-memoir__chapter::before,
.story-memoir__chapter::after {
  content: "";
  position: absolute;
  left: 50%;
  width: 4rem;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--color--ink-dark), transparent);
  transform: translateX(-50%);
}

.story-memoir__chapter::before { top: 1rem; }
.story-memoir__chapter::after  { bottom: 1rem; }

.story-memoir__chapter-head {
  text-align: center;
  margin-bottom: 2.5rem;
  padding-bottom: 1.75rem;
  border-bottom: 1px solid rgba(0, 0, 0, 0.1);
}

.story-memoir__title {
  font-size: 1.375rem;
  font-weight: 500;
  color: var(--color--ink);
  letter-spacing: 0.04em;
  line-height: 1.6;
}

.story-memoir__body {
  font-size: 1rem;
  line-height: 2.1;
  font-family: var(--font--serif);
}

.story-memoir__body p { margin-bottom: 1.5rem; }

.story-memoir__dropcap {
  float: left;
  font-family: var(--font--display);
  font-size: 4.5rem;
  line-height: 0.85;
  padding: 0.4rem 0.5rem 0 0;
  background: var(--gradient--accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  font-weight: 500;
}

.story-memoir__voice {
  text-align: center;
  font-size: 1.125rem;
  color: var(--color--ink);
  font-style: italic;
  padding: 1rem 0;
  border-top: 1px solid rgba(0, 0, 0, 0.08);
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  margin: 2rem 0 !important;
}

.story-memoir__close {
  font-weight: 500;
  color: var(--color--ink);
}

@media (min-width: 768px) {
  .story-memoir__chapter { padding: 4rem 4rem; }
  .story-memoir__title { font-size: 1.625rem; }
  .story-memoir__body { font-size: 1.0625rem; line-height: 2.2; }
  .story-memoir__voice { font-size: 1.375rem; }
}