:root {
    --background-color: #0D1117;
    --text-color: #7D8590;
    --link-color: #7289DA;
    --link-color-hover: #7289DA;
    --borders: 1.5px solid rgba(255, 255, 255, 0.075);
    --title-background-color: #010409;
    --title-border: 2px solid rgba(255, 255, 255, 0.075);
    /* Fixed properties, unchanged in different themes: */
    --primary-font: monospace;
    --secondary-font: Cambria, Cochin, Georgia, Times, 'Times New Roman', serif;
    /* Properties unique to this page: */
    --scroll-track-background-color: #010409;
  }

  .lightmode {
    --background-color: #F3F2EE;
    --text-color: #7C7C81;
    --link-color: #B450B0;
    --link-color-hover: rgba(180, 80, 176, 0.8); /* 80% opacity of #B450B0 */
    --borders: 1px solid lightgray;
    --title-background-color: white;
    --title-border: 1px solid lightgray;
    /* Properties unique to this page: */
    --scroll-track-background-color: rgba(255, 255, 255, 0.8);
  }
 
  html {  
    background: #0D1117; /* will change main background via javascript, not css properties */
    font-size: 16px;
    margin: 0;
    padding: 0;
  }
  
  .container {
    margin: 0 auto;
    width: 100%;
    max-width: 1500px;
    margin-top: 5vh;
    font-family: var(--primary-font);
    color: var(--text-color);
    /* color: black; */
  }
 
/* ___________________________________
   Main contents and navigation: */

  .grid-container {
    display: grid;
    grid-template-columns: 1fr 5fr 1fr;
    grid-template-rows: 9fr 1.5fr;
    height: 95vh; /* container fills screen without any overflow */
    grid-gap: 10px;
    grid-template-areas: 
    "menu-area text-area branding-area"
    "...       footer    ...";
  }
  
  .menu {
    grid-area: menu-area;
    writing-mode: vertical-lr;
    margin-left: 10%;
    font-size: 1.5rem;
  }

  .menu-link {
    text-decoration: none;
    color: rgba(124, 124, 129, 0.25); /* 25% opacity of #7C7C81; */
  }

  .menu-link:hover {
    color: var(--link-color-hover);
    cursor: pointer;
  }

  #active-page {
    color: var(--link-color);
    opacity: 1;
    writing-mode: horizontal-tb;
    font-family: var(--secondary-font);
    width: 2.5vw;
    text-decoration: none;
    font-size: 1.6rem;
  }

  .text {
    grid-area: text-area;
    font-size: 1.25rem;
    width: 70%;
  }

  .title {
    padding-left: 1%;
    padding-top: 0.5%;
    padding-right: 1%;
    padding-bottom: 0.5%;
    margin-left: -1%;
    margin-right: -1%;
    border-radius: 7.5px;
    background-color: var(--title-background-color);
    border: var(--title-border);
  }

  #title-text {
    opacity: 0.65;
  }

  .mode {
    float: right; /* this is causing <i> to go onto the next line */
    cursor: pointer;
    padding-right: 5px;
    opacity: 0.8;
  }

  .mode i:hover {
    opacity: 0.4;
  }

  .mode-instruction-text {  
    writing-mode: horizontal-tb;
    text-align: right;
    font-size: 1.2rem;
    margin-left: -25vw;
    color: var(--text-color);
    font-family: var(--secondary-font);
    padding-top: 3vh;
  }

  .mode-instruction-text-inset {
    font-family: var(--primary-font);
    font-size: 0.9rem;
  }

  .footer {
    font-size: 1rem;
    border-top: var(--borders);
    grid-area: footer;
    width: 70%;
  }

  footer a {
    text-decoration: none;
    color: var(--text-color);
  }

  footer a:hover {
    color: var(--link-color);
  }

  .footer-social-link {
    text-decoration: underline;
  }

  .footer-wording {
    float: right;
    font-family: var(--secondary-font);
  }

  .branding {
    grid-area: branding-area;
    display: flex;
    justify-content: space-between;
    writing-mode: vertical-rl;
    margin-right: 10%;
    margin-bottom: -5vh;
    height: 87.5vh;
  }

  .branding img {
    width: 3vw;
    height: auto;
  }

  .responsive-header {
    display: none;
  }

/* New code for About page: */

  .flex-container {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
  }

  .about-introduction {
    text-align: justify;
    font-size: 1rem;
    padding: 1.5vh 0 2vh 0;
  }

  .biography-container {
    display: grid;
    grid-template-columns: 1fr 1.25fr;
    border-top: var(--borders);
    column-gap: 2.5%;
    padding-top: 2.5vh;
    padding-bottom: 2.5vh;
  }

  .biography-container img {
    width: 100%;
    height: auto;
  }

  .biography-text {  
    font-size: 0.9rem;
    align-self: center;   
    margin-left: 1%;
    padding: 0 17.5px 0 15px;
    /* Scrollbar: */
    float: left;
    height: 200px;
    overflow-y: scroll;
    overflow-x: hidden;
  }

  .biography-text:hover {
    cursor: s-resize;
    margin-right: -17.5vw;
    transition: all 0.5s ease-in;
    text-align: justify;
    padding-top: 1vh;
    border-radius: 1%;
    border: 2.5px solid var(--text-color);
    height: 210px;
    font-size: 1rem;
  }

  .biography-name {
    font-size: 1.25rem;
    font-family: var(--secondary-font);
    text-align: left;
    font-weight: bold;
    font-style: italic;
  }

  .biography-title {
    font-size: 0.9rem;
    font-weight: normal;
    font-style: normal;
  }

  .biography-link a {
    text-decoration: underline;
    font-style: italic;
    color: var(--text-color);
  }

  .biography-link a:hover {
    opacity: 0.5;
  }

  .biography-grid-layout {
    grid-template-areas:
    "picture-area   text-area";  
  }

  .picture-grid-placement {
    grid-area: picture-area;
  }

  .text-grid-placement {
    grid-area: text-area;
  }
  
  .scrollbar-style::-webkit-scrollbar {
    width: 12px;
  }

  .scrollbar-style::-webkit-scrollbar-track {
    background: var(--scroll-track-background-color);
    border: 1px solid rgba(0,0,0,0.1);
    border-radius: 10px;
  }
  
  .scrollbar-style::-webkit-scrollbar-thumb {
    background: rgba(124, 124, 129, 0.75);
    border: 3px solid transparent;
    background-clip: content-box;
    border-radius: 10px; 
  }

/* __________________________________
   Responsive design - Tablet: */

  @media screen and (max-width: 992px) {

  html {
    overflow-x: hidden;
  }
  
  .container {
    width: 80%;
  }

  .grid-container {
    width: 100%;
    height: 85vh;
    padding-top: 3vh;
    grid-template-columns: 1fr;
    grid-template-rows: 1fr;
    grid-template-areas: 
      "text-area"
      "footer";
  }

  .responsive-header {
    width: 92.5%;
    padding-left: 7.5%;
    padding-bottom: 1.5vh;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: var(--borders);
    /* Make header top layer in document:  */
    z-index: 2;
    position: relative;
  }

  .responsive-logo {
    padding-right: 7.5%;
  }

  .burger div {
    width: 25px;
    height: 4px;
    margin: 4px;
    background: var(--link-color);
    transition: all 0.3s ease-in;
  }

  .responsive-mode {
    font-size: 1.25rem;
  }

  .responsive-header img {
    height: 4vh;
    width: auto;
  }

  .text {
    width: 90%;
    margin: 0 auto;
    z-index: 0;
    position: relative;
    padding-bottom: 5vh;
  }

  .mode {
    display: none;
  }

  .biography-text:hover {
    cursor: auto;
    margin-right: 0;
    transition: none;
    text-align: left;
    padding-top: 0;
    border: none;
    border-radius: 0;
    font-size: 0.9rem;
    height: 200px;
  }

  .picture-grid-placement {
    align-self: center; 
  }

  .branding {
    display: none;
  }

  .footer {
    width: 100%;
    padding-bottom: 4vh;
  }

/* ____________________
   Burger menu: */

  .menu {
    position: fixed;
    right: 0;
    top: 0;
    z-index: 1;
    height: 100vh;
    width: 100vw;
    background-color: var(--background-color);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    transform: translateX(100%);
    transition: transform 0.5s ease-in;
    writing-mode: horizontal-tb;
    font-size: 1.75rem;
  }

  .menu a {
    color: rgba(124, 124, 129, 1);
  }

  #active-page {
    padding-bottom: 1px;
    font-family: var(--primary-font);
    width: fit-content;
  }

  .nav-active {
    transform: translateX(0%);
  }

  .toggle .line1 {
    transform: rotate(-45deg) translate(-5px, 6px);
  }

  .toggle .line2 {
    opacity: 0;
  }

  .toggle .line3 {
    transform: rotate(45deg) translate(-5px, -6px);
  }
}

/* _________________________________
   Responsive design - Phone: */

  @media screen and (max-width: 576px) {

  html {
    font-size: 14px;
  }

  .container {
    width: 100%;
  }

  .responsive-header img {
    height: 6vh;
  }

  .biography-text {
    padding: 0 5px 0 0;
  }  

  .scrollbar {
    height: 175px;
  }

  .biography-text:hover {
    height: 175px;
  }

  .biography-title {
    display: block;
  }

  .footer {
    width: 90%;
    margin: auto;
  }

  .footer-wording {
    padding-top: 1vh;
  }  
}