html {
  font-size: 75%;
}

body {
  font-family: "Helvetica", "Arial", sans-serif;
  margin: 0;
  padding: 0;
  background-color: #fef6dc;
  color: #333;
  line-height: 1.7;
  width: 100%;
}

.header {
  text-align: center;
  padding: 3rem 0;
}

/* タイトル */
.header h1 {
  font-size: 3.2rem;
  margin-bottom: 2rem;
}

.icon-box img {
  border-radius: 10%;
  display: inline-block;
  width: 8rem;
  background-color: #ccc;
  margin-right: 3%;
  vertical-align: middle;
  box-shadow: 0 8px 12px rgba(0, 0, 0, 0.1);
}

.introduction {
  display: flex;
  flex-direction: row;
  text-align: center;
  align-items: center;
  justify-content: center;
}

.character {
  width: 8rem;
  height: 9rem;
}

.chara3 {
  margin-right: auto;
  margin-left: 0;
}

/* 吹き出し */
.speech-bubble {
  position: relative;
  background: #ffffff;
  font-size: 1.6rem;
  text-align: left;
  border-radius: 10px;
  padding: 2rem;
  max-width: 380px;
  line-height: 1.5;
  margin: 40px;
  box-shadow: 0 8px 12px rgba(0, 0, 0, 0.15);
}

.speech-bubble::before {
  content: "";
  position: absolute;
  top: 20px;
  left: -30px;
  width: 0;
  height: 0;
  border-top: 10px solid transparent;
  border-bottom: 10px solid transparent;
  border-right: 30px solid #ffffff;
}

/* 画面 */
.app-images img {
  margin-top: 1rem;
  margin-bottom: 1rem;
  height: 40rem;
}

/* アプリダウンロード */
.store-button {
  display: flex;
  flex-direction: column;
  justify-content: center;
  background-color: #ececec;
  width: 100%;
  height: 20vh;
}

h4 {
  font-size: 2rem;
  font-weight: bold;
  /* padding-top: 2rem; */
  margin-bottom: 1rem;
}

.store-button img {
  height: 5rem;
}

/* 機能紹介 */
h2 {
  text-align: center;
  color: #007bff;
  margin: 2rem;
  font-size: 3rem;
}

section {
  display: flex;
  flex-direction: row;
  text-align: center;
  margin: 9rem auto;
  width: 63rem;
  justify-content: space-between;
}

section:nth-child(odd) {
  flex-direction: row-reverse;
  justify-content: space-between;
}

section .screen {
  height: 45rem;
}

section:nth-child(odd) img {
  margin-left: 3rem;
}

section:nth-child(even) img {
  margin-right: 3rem;
}

section article {
  text-align: left;
  display: flex;
  flex-direction: column;
}

section article .section-number {
  font-size: 3.6rem;
  color: #007bff;
}

section article h3 {
  font-size: 2.4rem;
  font-weight: bold;
  margin-bottom: 1rem;
}

section article p {
  font-size: 1.6rem;
}

section article img {
  margin-top: auto;
  margin-left: auto;
}

.tab {
  display: inline-block;
  width: 2rem;
}

.footer {
  text-align: center;
}

.footer .contact a {
  color: #007bff;
  text-decoration: none;
  font-size: 1.6rem;
}

.footer .contact a:hover {
  text-decoration: underline;
}

.footer .contact p {
  font-size: 1.6rem;
  padding-bottom: 3rem;
}

.footer .copyright {
  background-color: #ffffff;
  padding: 2rem 0;
}

.footer .copyright p {
  font-size: 1.2rem;
}

@media (max-width: 780px) {
  html {
    font-size: 62.5%;
  }
}

@media (max-width: 650px) {
  html {
    font-size: 45%;
  }

  h1 {
    font-size: 1.8rem;
  }

  .speech-bubble {
    margin: 20px;
  }

  .app-images img {
    height: 30rem;
  }

  .store-button {
    height: 15vh;
  }
  section,
  section:nth-child(odd) {
    width: 90%;
  }

  section article .section-number {
    font-size: 2rem;
  }

  section article h3 {
    font-size: 1.6rem;
  }

  section img,
  section:nth-child(odd) .screen,
  section:nth-child(even) .screen {
    height: 35rem;
  }

  @media (max-width: 380px) {
    h1 {
      font-size: 1.3rem;
    }
  }
}