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

:root {
  --color-calculator: rgb(100, 100, 100);
  
  --color-text: white; 

  --color-calculator-button: rgb(130, 130, 130);
  --color-calculator-button-active: rgb(191, 191, 191);

  --color-operator-button: orange;
  --color-operator-button-active: rgb(200, 130, 0);

  --color-function-button: rgb(70, 70, 70);
  --color-function-button-active: rgb(130, 130, 130);
}

body {
  display: flex;
  flex-direction: column;
  align-items: center;
  background-color: var(--color-calculator-button-active);
  font-family: Arial, Helvetica, sans-serif;
  height: 100vh;
}

header, footer {
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--color-calculator);
  color: var(--color-text);
  text-align: center;
  height: 50px;
  width: 100vw;
}

main {
  flex-grow: 1;
}

svg {
  fill: var(--color-calculator-button-active);
  margin-right: 5px;
}

a {
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  color: var(--color-calculator-button-active);
}

a:hover > svg{
  fill: var(--color-text);
}

a:hover {
  color: var(--color-text);
}

.calculator-container {
  margin-top: 50px;
  background-color: var(--color-calculator);
  border: 1px solid black;
  border-radius: 8px;
}

.input-field {
  background-color: var(--color-calculator);
  border-radius: 8px 8px 0 0;
  color: var(--color-text);
  font-size: 2em;
  text-align: right;
  padding: 14px 2px 2px 2px;
  margin-bottom: 1px;
  height: 60px;
  width: 208px;
}

.grid-calculator-buttons {
  display: grid;
  gap: 1px;
  grid-template-columns: repeat(3, 50px) 55px; 
  grid-template-rows: repeat(5, 50px);
}

button {
  color: var(--color-text);
  border: none;
  font-size: 1em;
  padding: 1px;
  height: 50px;
  width: auto;
}

button:focus-visible {
  outline: none;
}

.grid-calculator-buttons button {
  background-color: var(--color-calculator-button);
}

.grid-calculator-buttons button:active,
.grid-calculator-buttons button.active {
  background-color: var(--color-calculator-button-active);
}

.grid-operator-buttons {
  display: grid;
  gap: 1px;
  grid-column: 4 / 5;
  grid-row: 1 / 6; 
}

.grid-operator-buttons button {
  background-color: var(--color-operator-button);
}

.grid-operator-buttons button:active, 
.grid-operator-buttons button.active {
background-color: var(--color-operator-button-active);
}

.operator-buttons-clicked {
  border: 1px solid var(--color-calculator);
}

#backspace, #clear, #negate {
  background-color: var(--color-function-button);
}

#clear {
  grid-column: 1 / 2;
  grid-row: 1 / 2;
}

#clear:active, #backspace:active, #negate:active,
#clear.active, #backspace.active, #negate.active {
  background-color: var(--color-function-button-active);
}

#button-zero {
  grid-column: 1 / 3;
  border-radius: 0 0 0 8px; 
}

#equal {
  border-radius: 0 0 8px 0; 
  border: none;
}