* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Lato", sans-serif;
}

:root {
  --black-color: #272a31;
  --ornage-color: #ec5242;
  --gray-color: #d3d3d3;
  --white-color: #fff;
}

html {
  font-size: 16px;
}

a {
  text-decoration: none;
}

body {
  background-image: url(../images/mobile-bg.jpg);
  background-repeat: no-repeat;
  background-size: cover;
  height: 88vh;
}

/* mobile menu */

.mobile-menu {
  position: fixed;
  top: 0;
  left: 0;
  display: flex;
  padding: 1.75rem;
  height: 100%;
  width: 100%;
  background-color: #3a3a3a;
  flex-direction: column;
  opacity: 0.9;
}

.mobile-menu .close-menu {
  align-self: flex-end;
}

.mobile-menu .mobile-menu-content {
  padding-left: 1.75rem;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  gap: 1.25rem;
}

.mobile-menu a {
  text-decoration: none;
  color: var(--gray-color);
  font-size: 2rem;
}

.mobile-menu a:hover {
  color: var(--ornage-color);
}

header {
  padding: 1.2rem 0 0 1.5rem;
}

/* about-hero section */

.about-hero {
  display: flex;
  flex-direction: column;
  padding: 2rem 2.4rem;
  align-items: center;
}

.hero-header {
  margin-bottom: 2rem;
}

.hero-header .greeting {
  color: var(--ornage-color);
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  text-align: center;
}

.hero-header .welcome {
  font-weight: 900;
  font-size: 2.4rem;
  color: var(--ornage-color);
}

.about-hero .about-text {
  font-size: 1rem;
  font-weight: 400;
  text-align: center;
  padding: 1rem 0.5rem;
  background-color: var(--white-color);
  line-height: 1.5rem;
  margin-bottom: 1.2rem;
}

.contact {
  display: flex;
  flex-direction: column;
  line-height: 1.2rem;
  justify-content: center;
  align-items: center;
}

.contact .contact-txt {
  font-size: 0.9rem;
  color: #7a7a7a;
  text-align: center;
}

.contact .contact-email {
  font-size: 0.9rem;
  font-weight: 700;
  color: #5f5f5f;
  text-align: center;
  justify-content: center;
  border-bottom: 1px solid #5f5f5f;
}

/* Logo info section */

.logo-info-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem 1.5rem;
  gap: 1.5rem;
  text-align: center;
}

.logo-info-wrapper .logo-underline {
  width: 2rem;
  border: 1px solid var(--ornage-color);
  margin: -0.5rem 0;
}

.logo-past-underline {
  width: 100%;
  border: 1px solid var(--gray-color);
  margin: 1rem 0;
}

.logo-info-wrapper .logo-image {
  width: 50%;
  border: 1px solid var(--gray-color);
}

.logo-info-wrapper .about-logo {
  color: #838383;
  font-size: 1rem;
  line-height: 1.75rem;
}

/* past conference */

.see-past-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem 2.4rem;
  gap: 1.5rem;
  text-align: center;
}

.see-past-wrapper .title-underline {
  width: 2rem;
  border: 1px solid var(--ornage-color);
  margin: -0.5rem 0;
}

.see-past-wrapper .about-past {
  color: #838383;
  font-size: 1rem;
  line-height: 1.75rem;
}

.past-image-container {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  margin: 1.2rem 0;
}

.past-conference img {
  width: 100%;
  height: 30vh;
}

.past-conference {
  cursor: pointer;
  position: relative;
}

.past-text > h2 {
  font-size: 2rem;
}

.past-text > p {
  font-size: 1.1rem;
}

.past-conference .past-description {
  background-color: var(--ornage-color);
  position: absolute;
  top: 0;
  left: 0;
  color: var(--white-color);
  -webkit-transition: all 0.3s ease-out;
  -moz-transition: all 0.3s ease-out;
  -o-transition: all 0.3s ease-out;
  -ms-transition: all 0.3s ease-out;
  transition: all 0.3s ease-out;
  opacity: 0.8;
  width: 100%;
  height: 100%;
  padding: 3rem 1.25rem;
  text-align: center;
}

.past-conference:hover .past-description {
  opacity: 0;
}

.past-conference .past-text {
  -moz-transition: all 0.3s ease-out;
  -o-transition: all 0.3s ease-out;
  -ms-transition: all 0.3s ease-out;
  transition: all 0.3s ease-out;
  font-size: 1em;
  opacity: 0.8;
  transition-delay: 0.3s;
  transition-duration: 0.3s;
}

.past-conference:hover .past-text,
.past-conference:focus .past-text {
  opacity: 1;
}

/* partner section */

.partner-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 5%;
  gap: 0.8rem;
  background-color: var(--black-color);
  color: var(--white-color);
}

.partner-wrapper .partner-title {
  margin-top: 2rem;
  font-size: 1.5rem;
  font-weight: 700;
  line-height: 2rem;
}

.partner-wrapper .title-underline {
  width: 3rem;
  border: 1px solid var(--ornage-color);
  margin-bottom: 2rem;
}

.partner-logo img {
  display: inline-flex;
  flex-wrap: wrap;
  width: 30%;
  max-width: 10rem;
}

/******** footer ********/

footer {
  display: flex;
  justify-content: space-evenly;
  align-items: center;
  padding: 1.6rem 2rem;
}

footer .footer-logo {
  width: 100px;
  height: 80px;
}

footer .copyright {
  color: #838383;
  font-weight: 700;
  font-size: 0.9rem;
}

.hidden {
  display: none;
}

.navbar-menu .logo,
.social-link-top,
.navbar-menu {
  display: none;
}

/* desktop version */
@media screen and (min-width: 768px) {
  .mobile-menu-icon {
    display: none;
  }

  .partner-wrapper {
    display: none;
  }

  .navbar-menu .logo,
  .social-link-top,
  .navbar-menu {
    display: block;
  }

  header {
    padding: 1rem 0 0;
  }

  body {
    margin-top: -1.2rem;
    background-image: url(../images/desktop_bg.png);
    background-size: cover;
    background-position: 50% 50%;
    max-height: 500px;
    width: 100%;
  }

  .about-hero {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    padding: 2.5rem 3rem;
  }

  .navbar-menu .logo img {
    display: block;
    width: 100%;
    height: 5rem;
  }

  .social-link-top {
    background-color: #3e3e3e;
  }

  .social-link-top ul {
    display: flex;
    justify-content: flex-end;
    list-style: none;
    padding: 0.5rem 0;
    gap: 1rem;
    margin-right: 12rem;
  }

  .menu li a {
    color: var(--black-color);
  }

  .social-link-top ul li a {
    color: var(--white-color);
  }

  .menu li a:hover,
  .menu li a:focus {
    color: var(--ornage-color);
  }

  .social-link-top ul li a:hover {
    color: var(--ornage-color);
  }

  .social-link-top ul li img:hover {
    transform: scale(1.1);
  }

  /* menu */

  .navbar-menu {
    display: flex;
    justify-content: space-around;
    align-items: center;
    background-color: var(--white-color);
    width: 100%;
    height: 5rem;
  }

  .navbar-menu .menu {
    list-style: none;
    display: flex;
    gap: 2rem;
  }

  .menu li#campaign a {
    color: var(--ornage-color);
    border: 4px solid var(--ornage-color);
    padding: 0.7rem;
  }

  .menu li#campaign a:hover {
    background-color: var(--ornage-color);
    color: var(--white-color);
    padding: 0.7rem;
  }

  .past-image-container {
    flex-direction: row;
  }

  .logo-info-wrapper .logo-image {
    width: 20%;
    max-width: 220px;
    height: auto;
  }

  footer {
    background-color: var(--black-color);
    color: var(--white-color);
    padding: 1.6rem 0;
  }

  .logo-info-wrapper {
    margin-top: 4rem;
  }

  .hero-header .welcome {
    font-weight: 900;
    font-size: 2rem;
  }

  .about-hero .about-text {
    width: 80%;
    max-width: 568px;
  }
}