body {
  background-color: #808080;
  color: #000000;
  font-family: sans-serif;
  min-width: 320px;
  max-width: 100vw;
  margin: 30px;
  padding: 30px;
  overflow-x: hidden; /* 横スクロールを防ぐ */
  box-sizing: border-box;
}

h1 {
  font-size: 36px;
}

h2 {
  font-size: 30px;
}

h3 {
  font-size: 20px;
}

header {
  display: flex;
  position: fixed;
  gap: 30px;
  width: 100%;
  height: 50px;
  background: #666666;
  top: 0;
  left: 0;
}

p, a {
  font-size: 16px;
  line-height: 2.5;
  word-wrap: break-word;
}

ul li {
  font-weight: bolder;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

.logo {
  width: auto;
  height: 40px;
  padding: 5px;
}

.logo:hover {
  filter: brightness(0.6);
}

.bold {
  font-weight: bold;
}

.side-group {
  display: flex;
  gap: 50px;
  flex-wrap: wrap;
  justify-content: center;
}

.side-left, .side-right {
  min-width: 300px;
  max-width: 40%;
}

.side-left {
  flex: 1;
}

.side-right {
  flex: auto;
}

.vertical-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.img-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  max-width: 100%;
}

.img-with-description {
  display: block;
  background-color: #cccccc;
  border-radius: 5px;
  padding: 5px;
  max-width: 300px;
  max-height: 450px;
}

.img-with-description p {
  color: #333333;
  text-align: center;
  font-size: 10px;
}

.keyboard {
  font-size: 16px;
  font-weight: bolder;
  background-color: #ffffff;
  border: 1px solid rgba(0, 0, 0, 0.5);
  border-radius: 5px;
  box-shadow: 5px 5px 5px rgba(0, 0, 0, 0.5);
  margin: 2px;
  padding: 5px 10px;
}

#thanks {
  text-align: center;
}

#how-to-use {
  max-width: 600px;
  margin: auto;
}

#image-overlay {
  animation: fadeIn 0.2s ease-in-out;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}