* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}

html,
body {
  max-width: 100vw;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  background-color: #FFEF9F;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='100%25'%3E%3Cdefs%3E%3ClinearGradient id='a' gradientUnits='userSpaceOnUse' x1='0' x2='0' y1='0' y2='100%25' gradientTransform='rotate(145,777,482)'%3E%3Cstop offset='0' stop-color='%23FFEF9F'/%3E%3Cstop offset='1' stop-color='%238AF1FF'/%3E%3C/linearGradient%3E%3Cpattern patternUnits='userSpaceOnUse' id='b' width='300' height='250' x='0' y='0' viewBox='0 0 1080 900'%3E%3Cg fill-opacity='0.1'%3E%3Cpolygon fill='%23444' points='90 150 0 300 180 300'/%3E%3Cpolygon points='90 150 180 0 0 0'/%3E%3Cpolygon fill='%23AAA' points='270 150 360 0 180 0'/%3E%3Cpolygon fill='%23DDD' points='450 150 360 300 540 300'/%3E%3Cpolygon fill='%23999' points='450 150 540 0 360 0'/%3E%3Cpolygon points='630 150 540 300 720 300'/%3E%3Cpolygon fill='%23DDD' points='630 150 720 0 540 0'/%3E%3Cpolygon fill='%23444' points='810 150 720 300 900 300'/%3E%3Cpolygon fill='%23FFF' points='810 150 900 0 720 0'/%3E%3Cpolygon fill='%23DDD' points='990 150 900 300 1080 300'/%3E%3Cpolygon fill='%23444' points='990 150 1080 0 900 0'/%3E%3Cpolygon fill='%23DDD' points='90 450 0 600 180 600'/%3E%3Cpolygon points='90 450 180 300 0 300'/%3E%3Cpolygon fill='%23666' points='270 450 180 600 360 600'/%3E%3Cpolygon fill='%23AAA' points='270 450 360 300 180 300'/%3E%3Cpolygon fill='%23DDD' points='450 450 360 600 540 600'/%3E%3Cpolygon fill='%23999' points='450 450 540 300 360 300'/%3E%3Cpolygon fill='%23999' points='630 450 540 600 720 600'/%3E%3Cpolygon fill='%23FFF' points='630 450 720 300 540 300'/%3E%3Cpolygon points='810 450 720 600 900 600'/%3E%3Cpolygon fill='%23DDD' points='810 450 900 300 720 300'/%3E%3Cpolygon fill='%23AAA' points='990 450 900 600 1080 600'/%3E%3Cpolygon fill='%23444' points='990 450 1080 300 900 300'/%3E%3Cpolygon fill='%23222' points='90 750 0 900 180 900'/%3E%3Cpolygon points='270 750 180 900 360 900'/%3E%3Cpolygon fill='%23DDD' points='270 750 360 600 180 600'/%3E%3Cpolygon points='450 750 540 600 360 600'/%3E%3Cpolygon points='630 750 540 900 720 900'/%3E%3Cpolygon fill='%23444' points='630 750 720 600 540 600'/%3E%3Cpolygon fill='%23AAA' points='810 750 720 900 900 900'/%3E%3Cpolygon fill='%23666' points='810 750 900 600 720 600'/%3E%3Cpolygon fill='%23999' points='990 750 900 900 1080 900'/%3E%3Cpolygon fill='%23999' points='180 0 90 150 270 150'/%3E%3Cpolygon fill='%23444' points='360 0 270 150 450 150'/%3E%3Cpolygon fill='%23FFF' points='540 0 450 150 630 150'/%3E%3Cpolygon points='900 0 810 150 990 150'/%3E%3Cpolygon fill='%23222' points='0 300 -90 450 90 450'/%3E%3Cpolygon fill='%23FFF' points='0 300 90 150 -90 150'/%3E%3Cpolygon fill='%23FFF' points='180 300 90 450 270 450'/%3E%3Cpolygon fill='%23666' points='180 300 270 150 90 150'/%3E%3Cpolygon fill='%23222' points='360 300 270 450 450 450'/%3E%3Cpolygon fill='%23FFF' points='360 300 450 150 270 150'/%3E%3Cpolygon fill='%23444' points='540 300 450 450 630 450'/%3E%3Cpolygon fill='%23222' points='540 300 630 150 450 150'/%3E%3Cpolygon fill='%23AAA' points='720 300 630 450 810 450'/%3E%3Cpolygon fill='%23666' points='720 300 810 150 630 150'/%3E%3Cpolygon fill='%23FFF' points='900 300 810 450 990 450'/%3E%3Cpolygon fill='%23999' points='900 300 990 150 810 150'/%3E%3Cpolygon points='0 600 -90 750 90 750'/%3E%3Cpolygon fill='%23666' points='0 600 90 450 -90 450'/%3E%3Cpolygon fill='%23AAA' points='180 600 90 750 270 750'/%3E%3Cpolygon fill='%23444' points='180 600 270 450 90 450'/%3E%3Cpolygon fill='%23444' points='360 600 270 750 450 750'/%3E%3Cpolygon fill='%23999' points='360 600 450 450 270 450'/%3E%3Cpolygon fill='%23666' points='540 600 630 450 450 450'/%3E%3Cpolygon fill='%23222' points='720 600 630 750 810 750'/%3E%3Cpolygon fill='%23FFF' points='900 600 810 750 990 750'/%3E%3Cpolygon fill='%23222' points='900 600 990 450 810 450'/%3E%3Cpolygon fill='%23DDD' points='0 900 90 750 -90 750'/%3E%3Cpolygon fill='%23444' points='180 900 270 750 90 750'/%3E%3Cpolygon fill='%23FFF' points='360 900 450 750 270 750'/%3E%3Cpolygon fill='%23AAA' points='540 900 630 750 450 750'/%3E%3Cpolygon fill='%23FFF' points='720 900 810 750 630 750'/%3E%3Cpolygon fill='%23222' points='900 900 990 750 810 750'/%3E%3Cpolygon fill='%23222' points='1080 300 990 450 1170 450'/%3E%3Cpolygon fill='%23FFF' points='1080 300 1170 150 990 150'/%3E%3Cpolygon points='1080 600 990 750 1170 750'/%3E%3Cpolygon fill='%23666' points='1080 600 1170 450 990 450'/%3E%3Cpolygon fill='%23DDD' points='1080 900 1170 750 990 750'/%3E%3C/g%3E%3C/pattern%3E%3C/defs%3E%3Crect x='0' y='0' fill='url(%23a)' width='100%25' height='100%25'/%3E%3Crect x='0' y='0' fill='url(%23b)' width='100%25' height='100%25'/%3E%3C/svg%3E");
  background-attachment: fixed;
  background-size: cover;
}

img {
  display: block;
}

a,
a:link,
a:focus,
a:visited {
  text-decoration: none;
  color: #4899e6;
}
a:hover {
  text-decoration: underline;
}

p {
  margin: 0;
  padding: 0;
}


#topbar {
  display: flex;
  align-items: center;
  padding: 0 120px;
  width: 100%;
  height: 80px;
  margin-bottom: 50px;
  background-color: rgba(255,255,255,0.8);
}
@media (max-width: 980px) {
  #topbar {
    justify-content: center;
    padding: 0 15px;
    height: 50px;
    margin-bottom: 25px;
  }
}
#topbar > a,
#topbar > a:link,
#topbar > a:visited {
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: stretch;
  font-size: 18px;
  letter-spacing: 5px;
  color: #777;
  text-decoration: none;
}
@media (max-width: 980px) {
  #topbar > a,
  #topbar > a:link,
  #topbar > a:visited {
    font-size: 15px;
  }
}

#main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  font-family: Rubik, Arial, sans-serif;
}

.hidden {
  opacity: 0;
  visibility: hidden;
  display: none;
  overflow: hidden;
  width: 0;
  height: 0;
}


/**
 *
 *  Header
 *
 */

#header {
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 15px 50px;
}
@media (max-width: 980px) {
  #header {
    margin: 0 10px 25px;
    flex-direction: column-reverse;
  }
}

#header-title {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-self: stretch;
  text-align: center;
  margin-right: 25px;
  font-size: 20px;
  line-height: 2;
  padding: 15px 20px;
  background-color: rgba(255, 255, 255, 0.8);
  border-radius: 10px;
  box-shadow: 1px 1px 3px rgba(0,0,0,0.5);
}
@media (max-width: 980px) {
  #header-title {
    margin-right: 0;
    font-size: 16px;
    padding: 10px;
    margin-top: 10px;
  }
}
#header-title > h1 {
  display: inline;
  font-size: 21px;
  padding: 0;
  margin: 0;
}
@media (max-width: 980px) {
  #header-title > h1 {
    font-size: 16px;
  }
}
#header-title > b {
  font-size: 24px;
}

#header-imageWrapper {
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 0 15px 1px rgba(255,255,255,0.5);
}
#header-imageWrapper > img {
  max-width: 420px;
  width: 100%;
}


/**
 *
 *  Stars / Difficulty
 *
 */

.stars {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 5px 0;
  border-radius: 10px;
  font-size: 14px;
  font-weight: bold;
  height: 32px;
}
.stars > div {
  display: flex;
  align-items: center;
  justify-content: center;
}
.stars > div:first-child {
  width: 70px;
}
.stars > div:last-child {
  flex: 1;
  padding-right: 15px;
  justify-content: flex-start;
}


/**
 *
 *  Filter
 *
 */

#filter {
  display: flex;
  background-color: #fff;
  box-shadow: 0 0 1px 0 rgba(0,0,0,0.5);
  max-width: 1080px;
  width: 100%;
  padding: 15px;
  border-radius: 10px;
  margin-bottom: 25px;
  user-select: none;
}
@media (max-width: 980px) {
  #filter {
    align-items: center;
    width: auto;
    align-self: stretch;
    margin: 0 10px 15px;
    flex-direction: column;
  }
}

#filter > div {
  display: flex;
  flex-direction: column;
  margin-right: 50px;
}
#filter > div:nth-child(3) {
  padding-right: 50px;
}
#filter > div:nth-child(4) {
  flex: 1;
}
@media (max-width: 980px) {
  #filter > div {
    padding-right: 0 !important;
    margin-right: 0;
    align-self: stretch;
  }
}

.filter-title {
  font-size: 12px;
  color: gray;
  text-decoration: underline;
  margin-bottom: 10px;
}

#filter-language {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  flex: 1;
  padding: 8px 0;
}
@media (max-width: 980px) {
  #filter-language {
    align-self: stretch;
    margin-bottom: 10px;
    flex-direction: row;
  }
}

.filter-language-option {
  display: flex;
  align-items: center;
  font-size: 12px;
  font-weight: bold;
  opacity: 0.5;
  padding-right: 20px;
  transition: opacity 0.2s;
  cursor: pointer;
}
.filter-language-option > img {
  margin-right: 10px;
}
.filter-language-option img:nth-child(1) {
  display: none;
}
@media (max-width: 980px) {
  .filter-language-option {
    padding-right: 0;
  }
}
.filter-language-option-selected {
  opacity: 1 !important;
}
.filter-language-option-selected img:nth-child(1) {
  display: inline-flex;
}
.filter-language-option-selected img:nth-child(2) {
  display: none;
}

#filter-difficulty {
  display: flex;
  flex-direction: column;
}
@media (max-width: 980px) {
  #filter-difficulty {
    margin-bottom: 10px;
  }
}

.filter-difficulty-option {
  display: flex;
  align-items: center;
  opacity: 0.5;
  cursor: pointer;
  transition: opacity 0.2s, box-shadow 0.2s;
}
.filter-difficulty-option > img:nth-child(1) {
  display: none;
}

.filter-difficulty-option-selected {
  opacity: 1 !important;
}
.filter-difficulty-option-selected > img:nth-child(1) {
  display: inline-flex;
}
.filter-difficulty-option-selected > img:nth-child(2) {
  display: none;
}

#filter-subject {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  max-height: 130px;
}
@media (max-width: 980px) {
  #filter-subject {
    flex-direction: row;
    align-items: center;
    max-height: none;
    margin-bottom: 15px;
  }
}

.filter-subject-option {
  display: flex;
  align-items: center;
  font-size: 12px;
  font-weight: bold;
  height: 32px;
  opacity: 0.5;
  padding-right: 20px;
  transition: opacity 0.2s;
  cursor: pointer;
}
.filter-subject-option img {
  margin-right: 4px;
}
.filter-subject-option img:nth-child(1) {
  display: none;
}
@media (max-width: 980px) {
  .filter-subject-option {
    padding: 0 15px;
    font-size: 11px;
  }
}

.filter-subject-option-selected {
  opacity: 1 !important;
}
.filter-subject-option-selected img:nth-child(1) {
  display: inline-flex;
}
.filter-subject-option-selected img:nth-child(2) {
  display: none;
}

#filter-search {
  display: flex;
  align-items: center;
}

#filter-search-input {
  flex: 1;
  padding: 0 10px;
  margin-left: 15px;
  border: 1px solid lightgray;
  border-radius: 4px;
  height: 28px;
  width: 100%;
}

/**
 *
 *  Questions
 *
 */

#questions {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 100%;
}
@media (max-width: 980px) {
  #questions {
    align-self: stretch;
    width: auto;
    margin: 0 10px;
  }
}

.question {
  width: 100%;
  max-width: 1080px;
  padding: 15px;
  border-radius: 10px;
  background-color: #fff;
  box-shadow: 0 0 1px 0 rgba(0,0,0,0.5);
  margin-bottom: 25px;
}

.question-header {
  display: flex;
  align-items: center;
  margin-bottom: 5px;
  font-size: 21px;
}

.question-stars {
  margin: 0 25px;
}
.question-stars .stars > div:first-child {
  width: auto;
  margin-right: 15px;
}

.question-subject {
  font-size: 12px;
  font-style: italic;
}

.question-title {
  font-size: 15px;
  text-align: justify;
  line-height: 1.5;
}
.question-title > div {
  margin-bottom: 5px;
}

.question-toggles {
  display: flex;
  align-items: center;
  font-size: 20px;
  margin-top: 10px;
}
.question-toggles > div {
  display: flex;
  align-items: center;
  cursor: pointer;
  margin-right: 35px;
}
.question-toggles > div > img {
  margin-left: 15px;
}

.question-solution,
.question-answer {
  text-align: justify;
  line-height: 1.5;
  font-size: 15px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out, padding 0.2s ease-out;
}
.question-solution > p,
.question-answer > p {
  display: flex;
  flex-direction: column;
}
.question-solution > p > i,
.question-answer > p > i {
  font-size: 11px;
  width: 50px;
}
.question-solution > p > span,
.question-answer > p > span {
  margin-bottom: 5px;
}

/**
 *
 *  Footer
 *
 */

#footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 40px 15px;
  background-color: rgba(255,255,255,0.7);
  width: 100%;
  border-top: 1px solid lightgray;
  margin-top: 100px;
}
@media (max-width: 980px) {
  #footer {
    margin-top: 25px;
  }
}

#footer-left,
#footer-right {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: #000;
}

#footer-left {
  font-size: 12px;
  line-height: 1.6;
}
#footer-left > a {
  color: #000;
}

#footer-right {
  font-size: 16px;
}
#footer-right > div > strong {
  margin-left: 5px;
}
#footer-right > img {
  margin-top: 8px;
  max-width: 100px;
}