:root {
  --my-light-gray: #5a5b5c;
  --my-gray: #3a3b3c;
  --my-dark-gray: #242526;
  --my-background: #18191a;
  --my-blue: #0866ff;
}

* {
  box-sizing: border-box;
  margin-inline: 0;
  margin-block: 0;
  padding-inline: 0;
  padding-block: 0;
  border-inline: 0;
  border-block: 0;
  color: white;
}

html {
  font-size: 14px;
}

body {
  background-color: var(--my-background);
}

.main-header {
  position: fixed;
  inset-inline-start: 0;
  inset-block-start: 0;
  block-size: 4rem;
  display: block flex;
  flex-direction: row;
  padding-inline: 1rem;
  background-color: var(--my-dark-gray);
  justify-content: space-between;
  inline-size: 100%;
}

.main-header__logo-and-search {
  display: block flex;
  flex: 0 0 auto;
}

.main-header__logo {
  display: block flex;
  align-items: center;
  margin-inline-end: 1rem;
}

.main-header__logo img {
  block-size: 70%;
}

.main-header__search-box {
  flex: 0 0 20%;
  display: block flex;
  align-items: center;
  position: relative;
}

.main-header__search-box > input[name="search"] {
  background-color: var(--my-gray);
  font-size: 1.25rem;
  block-size: 70%;
  border-radius: 2rem;
  padding-inline-end: 1rem;
  padding-inline-start: 2.25rem;
}

.main-header__search-box > input[name="search"]:focus {
  outline: 0;
}

.main-header__search-box::before {
  content: "";
  position: absolute;
  inset-inline-start: 10px;
  inset-block-start: 0;
  inset-block-end: 0;
  inline-size: 1.25rem;
  block-size: 70%;
  /* Note: because this is a pseudo element our align-items declaration does not work on it. */
  align-self: center;
  background: url("./assets/magnifier.svg") center / contain no-repeat;
}

.main-header__navbar {
  display: block flex;
  flex: 0 0 auto;
  margin-inline-end: 15rem;
}

.main-header__navbar > a {
  block-size: calc(100% - 0.5rem);
  justify-content: center;
  display: block flex;
  align-items: center;
  padding-inline: 2rem;
  margin-inline: 0.25rem;
  margin-block: 0.25rem;
}

.main-header__navbar > a:hover {
  background-color: var(--my-gray);
  border-radius: 1rem;
}

.main-header__navbar > a > img {
  block-size: 60%;
}

.main-header__navbar > .main-header__navbar--active {
  margin-block-end: 0;
  padding-block-end: 0.25rem;
  block-size: calc(100% - 0.25rem);
  border-block-end: 3px solid var(--my-blue);
}

.main-header__navbar > .main-header__navbar--active:hover {
  border-radius: 0;
  background-color: transparent;
}

.main-header__account-control-and-setting {
  flex: 0 0 auto;
  display: block flex;
}

.main-header__account,
.main-header__notifications,
.main-header__messenger,
.main-header__menu {
  display: block flex;
  flex: 0 0 auto;
  align-items: center;
  cursor: pointer;
  margin-inline-start: 0.5rem;
  background-color: var(--my-gray);
  border-radius: 3rem;
  margin-block: 0.5rem;
  padding-inline: 0.5rem;
}

.main-header__account:hover,
.main-header__notifications:hover,
.main-header__messenger:hover,
.main-header__menu:hover {
  background-color: var(--my-light-gray);
}

.main-header__account > img,
.main-header__notifications > img,
.main-header__messenger > img,
.main-header__menu > img {
  inline-size: 2rem;
}

.main-header__account > img {
  border-radius: 2rem;
}

.side-navbar {
  position: fixed;
  inline-size: 25%;
  inset-inline-start: 0;
  inset-block-start: 4rem; /* This 4rem comes from the header's block-size css property. */
  padding-inline-start: 2rem;
  padding-block-end: 4rem;
  min-block-size: 100%;
  /* Won't work without physical properties */
  overflow-y: auto;
  overflow-x: hidden;
  height: 100%;
  scrollbar-color: var(--my-gray) transparent;
  scrollbar-width: thin;
}

.side-navbar__links {
  margin-block-start: 1rem;
  list-style-type: none;
  display: block flex;
  flex-direction: column;
  inline-size: fit-content;
}

.side-navbar__links > li > button,
.side-navbar__links > li > a {
  text-decoration: none;
  display: block flex;
  align-items: center;
  padding-inline: 0.5rem;
  border-radius: 0.5rem;
  padding-block: 0.5rem;
}

.side-navbar__links > li > button {
  background-color: transparent;
  cursor: pointer;
  inline-size: 100%;
}

.side-navbar__links > li > button > img {
  background-color: var(--my-light-gray);
}

.side-navbar__links > li > button:hover,
.side-navbar__links > li > a:hover {
  background-color: var(--my-gray);
}

.side-navbar__links > li > button > img,
.side-navbar__links > li > a > img {
  block-size: 2rem;
  border-radius: 2rem;
  margin-inline-end: 0.25rem;
}

.side-navbar__legal {
  flex: 0 0 100%;
  margin-block: 1rem;
}

.side-navbar__legal > a {
  text-decoration: none;
}

.side-navbar__legal > a:hover {
  text-decoration: underline;
}

.side-navbar__legal__more {
  background-color: transparent;
  font-size: 1rem;
}

.side-navbar__copyright {
  font-size: 1rem;
}

.main-content {
  display: block flex;
  margin-inline: auto;
  margin-block: 4rem;
  padding-block-start: 2rem;
  width: 50%;
  flex-direction: column;
}

.complementary-sidebar {
  position: fixed;
  inset-block-start: 4rem;
  inset-inline-end: 0;
  inline-size: 20%;
  overflow-x: hidden;
  overflow-y: auto;
  height: 100%;
  scrollbar-color: var(--my-gray) transparent;
  scrollbar-width: thin;
  padding-block-end: 5rem;
}

.contacts,
.birthdays,
.sponsored,
.group-chats {
  display: block flex;
  flex-direction: column;
  padding-block: 1rem;
  border-block-end: 1px solid var(--my-gray);
}

.group-chats {
  border-block-end: 0;
}

.contacts > header,
.birthdays > header,
.sponsored > header,
.group-chats > header {
  margin-block-end: 0.5rem;
}

.contacts > header {
  display: block flex;
  justify-content: space-between;
}

.contacts > header > h1,
.birthdays > header > h1,
.sponsored > header > h1,
.group-chats > header > h1 {
  font-size: 1.5rem;
}

.contacts > header > h1 {
  flex: 0 0 auto;
}

.sponsored__ad {
  flex: 0 0 100%;
}

.sponsored__ad + .sponsored__ad {
  margin-block-start: 1rem;
}

.sponsored__ad > figure {
  flex: 0 0 auto;
  display: block flex;
  flex-direction: row;
  align-items: center;
}

.sponsored__ad > figure > img {
  inline-size: 10rem;
  margin-inline-end: 1rem;
  border-radius: 1rem;
}

.sponsored__ad > figure > figcaption {
  white-space: nowrap;
  overflow: hidden;
  block-size: 100%;
  text-overflow: ellipsis;
}

.sponsored__ad > figure > figcaption > p {
  color: var(--my-gray);
}

.birthdays > a {
  font-size: 1.25rem;
  text-decoration: none;
  padding-block: 0.5rem;
  padding-inline: 1rem;
}

.birthdays > a:hover {
  background-color: var(--my-gray);
  border-radius: 1rem;
}

.contacts__options,
.contacts__search {
  cursor: pointer;
  inline-size: 2rem;
  background-color: transparent;
}

.contacts__options:hover,
.contacts__search:hover {
  background-color: var(--my-gray);
  border-radius: 1rem;
}

.contacts__list {
  display: block flex;
  overflow-y: auto;
  flex-direction: column;
  align-items: start;
  list-style-type: none;
}

.contacts__list > li {
  inline-size: calc(100% - 1rem);
  margin-inline-end: 1rem;
}

.contacts__list > li > a {
  display: block flex;
  align-items: center;
  padding-inline: 0.5rem;
  padding-block: 0.5rem;
}

.contacts__list > li > a:hover {
  background-color: var(--my-gray);
  border-radius: 1rem;
}

.contacts__list > li > a > img {
  block-size: 2rem;
  border-radius: 1rem;
  margin-inline-end: 0.5rem;
}

.group-chats__create {
  background-color: transparent;
  position: relative;
  text-align: start;
  padding-block-start: 0.5rem;
  padding-inline-start: 2.5rem;
  cursor: pointer;
}

.group-chats__create:focus {
  outline: none;
}

.group-chats__create::before {
  content: "";
  position: absolute;
  inset-inline-start: 0;
  inset-block-start: 0;
  inset-block-end: 0;
  inline-size: 2rem;
  block-size: 2rem;
  background: url("./assets/plus-circle.svg") center / contain no-repeat;
  background-color: var(--my-gray);
  border-radius: 1rem;
}