:root {
  --border: 2px solid white;
  --padding: 20px;
  --margin: 5px;
  --border-radius: 5px;

  --light-blue: rgba(59, 130, 246, 0.15);
  --blue: rgb(147, 186, 248);
  --dark-blue: rgb(59, 130, 246);
}

* {
  padding: 0;
  margin: 0;
  font-family: "Courier New", Courier, monospace;
  font-size: x-large;
}

body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.calculator {
  background-color: var(--light-blue);
  padding: var(--padding);
  margin: var(--margin);
}

.btn {
  background-color: var(--blue);
  padding: var(--padding);
  margin: var(--margin);
  border: var(--border);
  border-radius: var(--border-radius);
  transition: background-color 0.2s ease, color 0.2s ease, transform 0.1s ease;
}

.btn:hover {
  background-color: var(--dark-blue);
  color: white;
  cursor: pointer;
}

.btn:active {
  transform: scale(0.97);
  background-color: rgb(30, 94, 190); /* slightly darker shade for feedback */
}

#clear {
  width: 100%;
}

.screen {
  display: flex;
}

#calc-screen {
  border: var(--border);
  border-radius: var(--border-radius);
  margin: var(--margin);
  padding: var(--padding);
  outline: 2px solid var(--light-blue);
  background-color: white;
  width: 100%;
}

.keyboard {
  display: flex;
}

.keyboard-left {
  display: flex;
  flex-direction: column;
  width: min-content;
}

.zero-dot-equal {
  width: max-content;
}

.number-container {
  display: flex;
  flex-wrap: wrap;
}

.operators-container {
  display: flex;
  flex-direction: column;
}

/* media query for mobile devices */
@media (max-width: 480px) {
  :root {
    --padding: 10px;
    --margin: 3px;
  }

  * {
    font-size: medium;
  }

  .btn {
    padding: 12px;
    font-size: 1rem;
  }
}