body {
  font-weight: 400;
}

main {
  padding: 50px;
}

main h1 {
  font-weight: 400;
  text-align: center;
}

nav {
  display: block;
  position: fixed;
  background-color: #ffffff;
  width: 220px;
  top: 0;
  left: -300px;
  bottom: 0;
  transition: all 0.5s;
  z-index: 3;
  opacity: 0;
}

.open nav {
  left: 0;
  opacity: 1;
}

nav .inner {
  padding: 25px;
}

nav .inner ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

nav .inner ul li {
  margin: 0;
  border-bottom: 1px solid #333;
}

nav .inner ul li a {
  display: block;
  color: #333;
  font-size: 14px;
  padding: 1rem;
  text-decoration: none;
  transition-duration: 0.2s;
}

nav .inner ul li a:hover {
  background: #e4e4e4;
}

.toggle-btn {
  display: block;
  position: fixed;
  top: 30px;
  right: 30px;
  width: 30px;
  height: 30px;
  z-index: 3;
  cursor: pointer;
}

.toggle-btn span {
  position: absolute;
  display: block;
  left: 0;
  width: 30px;
  height: 2px;
  background-color: #333;
  transition: all 0.5s;
  border-radius: 4px;
}

.toggle-btn span:nth-child(1) {
  top: 4px;
}
.toggle-btn span:nth-child(2) {
  top: 14px;
}
.toggle-btn span:nth-child(3) {
  bottom: 4px;
}

.open .toggle-btn span {
  background-color: #fff;
}

.open .toggle-btn span:nth-child(1) {
  transform: translateY(10px) rotate(-315deg);
}

.open .toggle-btn span:nth-child(2) {
  opacity: 0;
}

.open .toggle-btn span:nth-child(3) {
  transform: translateY(-10px) rotate(315deg);
}

#mask {
  display: none;
  transition: all 0.5s;
}

.open #mask {
  display: block;
  background: #000;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  position: fixed;
  opacity: 0.8;
  z-index: 2;
  cursor: pointer;
}

	/* 2カラムサイトにする */
	.wrapper {
	    width: 80%;
	    display: flex;
	    margin: 20px auto;
	    justify-content: center;
	}

	.maine, .sid {
	    padding: 20px;
	}

	.main {
	    background: pink;
	    width: 90%;
	    margin-right: 20px;
	}

	.side {
	    background: skyblue;
	    width: 20%;
	}

	.side p, ul {
	    background-color: #f0f0f0;
	    padding: 30px;
	}

	/* 2カラムコンテンツにする */

	.archive {
	    display: flex;
	    flex-wrap: wrap;
	    justify-content: space-around;
	}

	.archive div {
	    margin-bottom: 3rem;
	    padding: 3rem;
	    width: 35%;
	    background-color: #f0f0f0;
	}

	.archive img {
	    display: block;
	    margin-bottom: 3rem;
	    width: 100%;
	    height: auto;
	}

	@media screen and (max-width: 768px) {
	    .wrapper {
	        flex-direction: column;
	        width: 100%;
	    }
	    .main, .side {
	        box-sizing: border-box;
	        width: 100%;
	        margin: 0;
	    }
	    .archive div {
	        width: 70%;
	        margin: 20px auto;
	    }
	}