style.css

@import url("https://fonts.googleapis.com/css2?family=Tinos:ital,wght@0,400;0,700;1,400;1,700&display=swap");

:root {
  --equals-margin: 11px;
  --num-input-size: 40px;
  --dark: #282830;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Firefox */
input[type="number"] {
  -moz-appearance: textfield;
}

input[type="number"] {
  padding: 2px;
  text-align: center;
  max-width: 100vw;
}

* {
  font-family: "Tinos", serif;
  outline: none;
  border-radius: 2px;
  box-shadow: none;
  border: none;
}

button,
input {
  border: 1px solid var(--dark);
  box-shadow: 2px 2px 2px 2px #ccc;
}

body {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  background-color: #faf0e6;
}

header {
  text-align: center;
  margin: 30px;
  margin-top: 50px;
  font-size: 1.5rem;
}

main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  margin: 0 10vw;
  gap: 20px;
}

main .equations {
  display: flex;
  flex-direction: column;
  justify-content: center;
  text-align: center;
}

main .eqn {
  margin: 10px;
}

main .eqn input {
  width: var(--num-input-size);
  aspect-ratio: 1 / 1;
}

main .eqn span {
  width: 30px;
  aspect-ratio: 1 / 1;
  font-size: 100%;
  margin: 8px;
}

main .eqn .equals {
  margin-right: var(--equals-margin);
}

main .calc-btn:hover {
  cursor: pointer;
  background-color: #fafafa;
}

main .calc-btn {
  min-width: 150px;
  min-height: 35px;
  background-color: white;
}

main .calc-btn {
  transform: translate(3px, 3px);
}

.solution {
  width: 70vw;
  min-height: 170px;
  margin: 50px auto;
  border: 1px solid black;
  position: relative;
}

.solution .bg {
  position: absolute;
  background-image: url("./img/texture.jpg");
  top: 0;
  left: 0;
  width: 70vw;
  min-height: 170px;
  opacity: 60%;
}

.solution .content {
  margin: 20px 35px;
  position: absolute;
}