/* ---------- リセット ---------- */

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

ol,
ul {
  list-style: none;
}

/* ---------- 変数 ---------- */

:root {
  --c-text: #1d1f23;
  --c-sub: #5f6670;
  --c-white: #ffffff;
  --c-bg-soft: #f4f6f8;
  --c-line: #e1e6ec;
  --c-accent: #1d9bf0;
  --c-dark: #0f1419;
  --c-dark-sub: #9aa6b2;
  --c-code-text: #e7e9ea;
  --font-base: system-ui, -apple-system, "Hiragino Sans", "Noto Sans JP", sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  --line: max(1px, 0.1rem);
  --radius: 1.2rem;
  --inner-width: 96rem;
  --inner-gutter: 4rem;
  --flow-gap: 3.2rem;
}

/* PC は 1440px、SP は 375px のときに 1rem = 10px（リキッドレイアウト） */
html {
  font-size: calc(100vw / 144);
}

@media (max-width: 767px) {
  html {
    font-size: calc(100vw / 37.5);
  }

  :root {
    --inner-gutter: 2rem;
    --flow-gap: 2.4rem;
  }
}

body {
  background: var(--c-white);
  color: var(--c-text);
  font-family: var(--font-base);
  font-size: 1.6rem;
  line-height: 1.8;
}

code {
  font-family: var(--font-mono);
}

:not(pre) > code {
  padding: 0.2rem 0.6rem;
  border-radius: 0.4rem;
  background: var(--c-bg-soft);
  font-size: 0.9em;
}

.inner {
  width: min(var(--inner-width), 100% - var(--inner-gutter) * 2);
  margin-inline: auto;
}

/* ---------- ヒーロー ---------- */

.hero {
  position: relative;
  overflow: hidden;
  padding-block: 12rem 11rem;
  background: var(--c-dark);
  color: var(--c-white);
}

.hero::before {
  content: "";
  position: absolute;
  top: -24rem;
  right: -16rem;
  width: 64rem;
  height: 64rem;
  border-radius: 50%;
  background: radial-gradient(circle, rgb(29 155 240 / 0.45), transparent 70%);
}

.hero .inner {
  position: relative;
}

.hero__label {
  color: var(--c-accent);
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.hero__title {
  margin-top: 2rem;
  font-size: 6.4rem;
  line-height: 1.3;
  letter-spacing: 0.02em;
}

.hero__lead {
  margin-top: 3.2rem;
  color: var(--c-dark-sub);
  font-size: 1.9rem;
}

.hero__url {
  color: var(--c-white);
  font-family: var(--font-mono);
  font-size: 0.9em;
}

/* ---------- セクション ---------- */

.section {
  margin-top: 10rem;
}

.section__title {
  font-size: 3.2rem;
  line-height: 1.4;
}

.section__lead {
  margin-top: 2rem;
  color: var(--c-sub);
}

/* しくみ */

.flow {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--flow-gap);
  margin-top: 4rem;
}

.flow__item {
  position: relative;
  padding: 2.8rem 2rem;
  border-radius: var(--radius);
  background: var(--c-bg-soft);
}

.flow__item:not(:last-child)::after {
  content: "→";
  position: absolute;
  top: 50%;
  right: calc(var(--flow-gap) / -2);
  transform: translate(50%, -50%);
  color: var(--c-accent);
  font-size: 2rem;
  font-weight: 700;
}

.flow__num {
  display: grid;
  place-items: center;
  width: 3.2rem;
  height: 3.2rem;
  border-radius: 50%;
  background: var(--c-accent);
  color: var(--c-white);
  font-weight: 700;
  line-height: 1;
}

.flow__title {
  margin-top: 1.6rem;
  font-size: 1.7rem;
  font-weight: 700;
  line-height: 1.5;
}

.flow__note {
  margin-top: 0.8rem;
  color: var(--c-sub);
  font-size: 1.3rem;
  line-height: 1.7;
  overflow-wrap: anywhere;
}

.points {
  margin-top: 4rem;
}

.points__item {
  position: relative;
  padding-left: 2.4rem;
}

.points__item + .points__item {
  margin-top: 1.2rem;
}

.points__item::before {
  content: "";
  position: absolute;
  top: calc(0.9em - 0.4rem);
  left: 0.4rem;
  width: 0.8rem;
  height: 0.8rem;
  border-radius: 50%;
  background: var(--c-accent);
}

/* 参加の準備 */

.steps {
  margin-top: 4rem;
  counter-reset: step;
}

.steps__item {
  position: relative;
  padding: 3.2rem 3.2rem 3.2rem 10rem;
  border: var(--line) solid var(--c-line);
  border-radius: var(--radius);
  counter-increment: step;
}

.steps__item + .steps__item {
  margin-top: 2.4rem;
}

.steps__item::before {
  content: counter(step);
  position: absolute;
  top: 3.2rem;
  left: 3.2rem;
  display: grid;
  place-items: center;
  width: 4rem;
  height: 4rem;
  border-radius: 50%;
  background: var(--c-dark);
  color: var(--c-white);
  font-weight: 700;
  line-height: 1;
}

.steps__title {
  font-size: 2rem;
  line-height: 1.5;
}

.steps__text {
  margin-top: 1.2rem;
}

.steps__list {
  margin-top: 1.2rem;
}

.steps__list-item {
  position: relative;
  padding-left: 2rem;
}

.steps__list-item + .steps__list-item {
  margin-top: 0.6rem;
}

.steps__list-item::before {
  content: "";
  position: absolute;
  top: calc(0.9em - 0.3rem);
  left: 0.3rem;
  width: 0.6rem;
  height: 0.6rem;
  border-radius: 50%;
  background: var(--c-sub);
}

.code {
  margin-top: 1.6rem;
  padding: 2rem 2.4rem;
  overflow-x: auto;
  border-radius: 0.8rem;
  background: var(--c-dark);
  color: var(--c-code-text);
  font-size: 1.4rem;
  line-height: 1.9;
}

/* ふだんの使い方 */

.usage {
  margin-top: 4rem;
  border-bottom: var(--line) solid var(--c-line);
}

.usage__row {
  display: grid;
  grid-template-columns: 26rem 1fr;
  gap: 3.2rem;
  padding-block: 2.4rem;
  border-top: var(--line) solid var(--c-line);
}

.usage__when {
  font-weight: 700;
}

.usage__note {
  display: block;
  margin-top: 0.4rem;
  color: var(--c-sub);
  font-size: 1.4rem;
}

/* 守ること */

.rules {
  margin-top: 4rem;
}

.rules__item {
  position: relative;
  padding-left: 4rem;
}

.rules__item + .rules__item {
  margin-top: 2.8rem;
}

.rules__item::before {
  content: "✓";
  position: absolute;
  top: 0;
  left: 0;
  display: grid;
  place-items: center;
  width: 2.8rem;
  height: 2.8rem;
  border-radius: 50%;
  background: var(--c-accent);
  color: var(--c-white);
  font-size: 1.4rem;
  font-weight: 700;
  line-height: 1;
}

.rules__title {
  font-weight: 700;
}

.rules__text {
  margin-top: 0.4rem;
  color: var(--c-sub);
}

/* ---------- フッター ---------- */

.footer {
  margin-top: 12rem;
  padding-block: 4rem;
  background: var(--c-bg-soft);
}

.footer__text {
  color: var(--c-sub);
  font-size: 1.3rem;
}

/* ---------- SP ---------- */

@media (max-width: 767px) {
  body {
    font-size: 1.5rem;
  }

  .hero {
    padding-block: 8rem 7rem;
  }

  .hero::before {
    top: -12rem;
    right: -16rem;
    width: 32rem;
    height: 32rem;
  }

  .hero__label {
    font-size: 1.2rem;
  }

  .hero__title {
    font-size: 3.4rem;
  }

  .hero__lead {
    margin-top: 2.4rem;
    font-size: 1.5rem;
  }

  .section {
    margin-top: 7.2rem;
  }

  .section__title {
    font-size: 2.4rem;
  }

  .flow {
    grid-template-columns: 1fr;
    margin-top: 3.2rem;
  }

  .flow__item:not(:last-child)::after {
    content: "↓";
    top: auto;
    right: 50%;
    bottom: calc(var(--flow-gap) / -2);
    transform: translate(50%, 50%);
    font-size: 1.6rem;
  }

  .steps__item {
    padding: 2.4rem 2rem 2.4rem 6.4rem;
  }

  .steps__item::before {
    top: 2.4rem;
    left: 2rem;
    width: 3.2rem;
    height: 3.2rem;
  }

  .steps__title {
    font-size: 1.7rem;
  }

  .code {
    padding: 1.6rem;
    font-size: 1.2rem;
  }

  .usage__row {
    grid-template-columns: 1fr;
    gap: 0.8rem;
    padding-block: 2rem;
  }

  .footer {
    margin-top: 8rem;
  }
}