html {
  scroll-behavior: smooth;
}

* {
  padding: 0;
  margin: 0;
  font-family: 'Varela Round', sans-serif;
}

header {
  width: 100%;
  position: fixed;
}

header > .nav {
  background-color: #007582;
  display: flex;
  align-items: center;
  padding: 10px;
  justify-content: space-between;
}

.nav a {
  text-decoration: none;
  color: #fff;
  font-weight: bold;
  margin: 0 15px;
}

#presentation {
  background: linear-gradient(rgba(0, 0, 0, 0.7), rgba(0, 0, 0, 0.7)), url("img/Arduino-section-1.jpg"), no-repeat;
  background-size: cover;
  background-repeat: no-repeat;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 50px;
  color: #fff;
  font-weight: 900;
  flex-direction: column;
  width: 100%;
}

#presentation .description {
  font-size: 12px;
  margin-top: 15px;
  font-weight: 100;
}

#history {
  height: 160vh;
  display: flex;
  flex-direction: row;
  justify-content: center;
  margin: 50px 20px;
  border-top: rgb(128, 128, 128) solid 1px;
  border-bottom: rgb(128, 128, 128) solid 1px;
}

.history-accordion {
  margin-right: auto;
  border-right: rgb(128, 128, 128) solid 1px;
  padding: 0 40px;
  height: 149vh;
}

.accordion {
  background-color: rgb(232, 255, 244);
  color: #444;
  cursor: pointer;
  padding: 18px;
  width: 100%;
  text-align: left;
  border: none;
  outline: none;
  transition: 0.4s;
}

.active, .accordion:hover {
  background-color: #00a2b4;
}

.panel {
  padding: 0 18px;
  background-color: white;
  max-height: 0;
  overflow: hidden;
  transition: max-height .2s ease-out;
}

#history > div.history-accordion {
  width: 60%;
}

button.accordion {
  border-bottom: rgb(209, 209, 209) solid 1px;
}

.history-accordion > div:first-child {
  margin: 50px 0px;
  color: #000;
  font-weight: bold;
  line-height: 20px;
  font-size: 20px;
}

#hardware {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 70vh;
  border-bottom: rgb(128, 128, 128) solid 1px;
}

#hardware > div {
  width: 75%;
}

#hardware > div > h1 {
  letter-spacing: 2px;
  font-weight: bolder;
  font-size: 34px;
  margin-bottom: 10px;
  text-align: center;
}

#hardware > div > div {
  margin-bottom: 30px;
  text-align: center;
}

#software {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 70vh;
}

#software h1 {
  margin-bottom: 15px;
}

.content-download {
  display: flex;
}

.download {
  padding: 28px;
  flex: 60% 1;
  background-color: #ededed;
}

.download img {
  width: 72px;
  margin-right: 28px;
}
.download h2 {
  display: flex;
  flex-direction: row;
  align-items: center;
}

.options {
  padding: 28px;
  background-color: #007582;
  flex: 33% 1;
  flex-direction: column;
  color: #fff;
}

.options > div {
  margin-bottom: 12px;
}

.options > div > a {
  display: flex;
  color: #fff;
  text-decoration: none;
}

.options > div > a > span:first-child {
  font-weight: bold;
}

@media only screen and (max-width: 900px) {
  #history {
    justify-content: center;
    align-items: start;
    height: 220vh;
  }

  #history > div {
    margin: 0;
    border: none;
  }
}