body {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  height: 100vh;
  margin: 0px;
  font-family: Helvetica, sans-serif;
}

header {
  background-color: #313c8c;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
  transition: all 0.5s ease;
}

header:hover {
  box-shadow: 0 0 15px rgba(0, 0, 0, 0.7);
}

.header {
  display: flex;
  justify-content: center;
  align-items: center;
}

.header-logo {
  margin: 15px 36px 15px 46px;
  width: 70px;
  display: flex;
  justify-content: center;
  align-items: center;
}

.header-text > h1,
.header-text > h1 > a {
  color: white;
  font-size: 24pt;
  text-decoration: none;
}

.menu {
  display: flex;
  align-items: center;
  justify-content: center;
}

.menu > a {
  font-size: 18pt;
  margin-right: 40px;
  color: white;
  text-decoration: none;
}

main {
  display: flex;
  flex-wrap: wrap-reverse;
  justify-content: space-around;
  align-items: center;
  margin: 20px;
}

article {
  align-self: center;
  margin: 20px;
  max-width: 900px;
}

article a {
  color: #0366d6;
  text-decoration: none;
}
article a:visited {
  color: #0366d6;
}
article a:hover {
  color: #0366d6;
  text-decoration: underline;
}

article pre {
  background-color: #f6f8fa;
  border-radius: 3px;
  font-size: 85%;
  line-height: 1.45;
  overflow: auto;
  padding: 16px;
}

article code {
  font-size: 85%;
  margin: 0;
  word-wrap: break-word;
  padding: 0.2em 0.4em;
  font-family: SFMono-Regular, Consolas, Liberation Mono, Menlo, Courier,
    monospace;
}

article img {
  max-width: 100%;
}

article p {
  line-height: 24px;
  font-weight: 400;
  font-size: 16px;
  color: #24292e;
}

article ul {
  margin-top: 0;
}

article li {
  color: #24292e;
  font-size: 16px;
  font-weight: 400;
  line-height: 1.5;
}

article h1,
article h2,
article h3 {
  border-bottom: 1px solid #eaecef;
  color: #111;
}

.left {
  min-width: 200px;
}

.demo {
  background-color: black;
  padding: 20px 5px 20px 5px;
  border-radius: 20px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
  margin: 40px;
}

.demo > video {
  height: 65vh;
  border-radius: 10px;
}

.right {
  width: 90%;
  max-width: 720px;
}

.bukovki {
  font-size: large;
  background-color: #eee;
  padding: 20px;
  border-radius: 20px;
}

.links {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.links-header {
  text-align: center;
  margin-top: 40px;
  margin-bottom: 20px;
}

.link {
  width: 100%;
  max-width: 400px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 8px;
  padding: 8px 8px 8px 0px;
  box-shadow: 0 0 8px rgba(0, 0, 0, 0.5);
  height: 60px;
  color: white;
  text-align: center;
  text-decoration: none;
  font-size: 20pt;
  transition: all 0.3s ease;
  cursor: pointer;
}

.link:hover {
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.7);
  opacity: 85%;
}

.link:active {
  box-shadow: 0 0 10px rgba(0, 0, 0, 1);
  opacity: 70%;
}

.link > svg {
  height: 40px;
  padding: 10px;
  border-right: medium solid white;
}

.link > div {
  flex-grow: 2;
}

#link-vk {
  background-color: #4a76a8;
}

#link-tg {
  background-color: #28a8e9;
}

#link-viber {
  background-color: #665cac;
}

footer {
  background-color: #333;
  padding: 10px;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
}

footer > a {
  color: #ccc;
  margin-right: 20px;
}

#viber-error {
  visibility: hidden;
  position: fixed;
  z-index: 10;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgba(0, 0, 0, 0.4);
  display: flex;
  justify-content: center;
  align-items: center;
}

.viber-error-box {
  background-color: white;
  padding: 40px;
  border-radius: 20px;
  max-width: 50vw;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.viber-error-box > h3 {
  margin-top: 0px;
}

.viber-error-box > img {
  image-rendering: crisp-edges;
  image-rendering: pixelated;
  margin: 40px;
}

@media (max-width: 800px) {
  .header-logo {
    width: 40px;
  }

  .header-text > h1,
  .header-text > h1 > a {
    font-size: 16pt;
  }

  .menu > a {
    font-size: 12pt;
  }

  article {
    align-self: unset;
    margin: 10px;
  }
}

@media (max-width: 640px) {
  .menu {
    margin: 5px 20px 20px 20px;
    width: 100%;
  }

  .header-logo {
    margin: 10px 18px 10px 20px;
  }

  .demo {
    margin: 40px 10px 40px 10px;
  }
}