@import url("https://fonts.googleapis.com/css2?family=Raleway:wght@100..900&display=swap");

* {
  box-sizing: border-box;
}

body {
  font-family: Raleway, Arial, sans-serif;
  margin: 0;
  padding: 20px;
}

.container {
  max-width: 1000px;
  margin: 0 auto;
}

.photo-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

@media (max-width: 800px) {
  .photo-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (max-width: 620px) {
  .photo-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

div.photo-box {
  /* background-color: #d0d0d0;*/
  padding: 10px;
}
div.photo-title {
  background-color: #caEEf9;
  padding: 7px;
  font-weight: bold;
  border-top-left-radius: 14px;
  border-top-right-radius: 14px;
  text-align: center;
}

img.mathtalk-thumbnail {
  border-bottom-left-radius: 14px;
  border-bottom-right-radius: 14px;
  width: 100%;
}

img.mathtalk {
  max-width: 100%;
  text-align: center;
  max-height: 75%;
}

#flip-card-checkbox {
  display: none;
}

.flip-card-label {
  position: absolute;
  top: 0;
  right: 0;
  padding: 10px 15px;
  background-color: rgb(0, 14, 207);
  cursor: pointer;
  z-index: 10;
  color: white;
  font-size: 1.7rem;
}

.flip-card-label:hover {
  background-color: rgb(0, 10, 150);
}

.flip-card {
  background-color: transparent;
  width: 100%;
  max-width: 900px;
  perspective: 1000px;
  position: relative;
}

.flip-card-inner {
  position: relative;
  width: 100%;
  text-align: center;
  transition: transform 0.8s;
  transform-style: preserve-3d;
}

#flip-card-checkbox:checked ~ .flip-card-inner {
  transform: rotateY(180deg);
}

.flip-card-front,
.flip-card-back {
  width: 100%;
  -webkit-backface-visibility: hidden; /* Safari */
  backface-visibility: hidden;
}

.flip-card-front {
  color: black;
}

.flip-card-back {
  background-color: rgb(208, 215, 255);
  color: black;
  transform: rotateY(180deg);
  padding: 20px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  font-size:1.5em
}

.flip-card-back > * {
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}