/* CSS Custom Properties for Theme 1 (Default) */
:root {
  /* Theme 1 Colors */
  --main-bg: hsl(222, 26%, 31%);
  --toggle-keypad-bg: hsl(223, 31%, 20%);
  --screen-bg: hsl(224, 36%, 15%);

  --key-bg-1: hsl(225, 21%, 49%);
  --key-shadow-1: hsl(224, 28%, 35%);

  --key-bg-2: hsl(6, 63%, 50%);
  --key-shadow-2: hsl(6, 70%, 34%);

  --key-bg-3: hsl(0, 0%, 90%);
  --key-shadow-3: hsl(28, 16%, 65%);

  --text-1: hsl(221, 14%, 31%);
  --text-2: hsl(0, 100%, 100%);

  /* Typography */
  --font-size: 32px;
  --font-family: "League Spartan", sans-serif;
  --font-weight: 700;
}

/* Theme 2 */
.theme-2 {
  --main-bg: hsl(0, 0%, 90%);
  --toggle-keypad-bg: hsl(0, 5%, 81%);
  --screen-bg: hsl(0, 0%, 93%);

  --key-bg-1: hsl(185, 42%, 37%);
  --key-shadow-1: hsl(185, 58%, 25%);

  --key-bg-2: hsl(25, 98%, 40%);
  --key-shadow-2: hsl(25, 99%, 27%);

  --key-bg-3: hsl(45, 7%, 89%);
  --key-shadow-3: hsl(35, 11%, 61%);

  --text-1: hsl(60, 10%, 19%);
  --text-2: hsl(0, 100%, 100%);
}

/* Theme 3 */
.theme-3 {
  --main-bg: hsl(268, 75%, 9%);
  --toggle-keypad-bg: hsl(268, 71%, 12%);
  --screen-bg: hsl(268, 71%, 12%);

  --key-bg-1: hsl(281, 89%, 26%);
  --key-shadow-1: hsl(285, 91%, 52%);

  --key-bg-2: hsl(176, 100%, 44%);
  --key-shadow-2: hsl(177, 92%, 70%);

  --key-bg-3: hsl(268, 47%, 21%);
  --key-shadow-3: hsl(290, 70%, 36%);

  --text-1: hsl(198, 20%, 13%);
  --text-2: hsl(52, 100%, 62%);
}

/* Reset and Base Styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-family);
  font-weight: var(--font-weight);
  background-color: var(--main-bg);
  color: var(--text-2);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 24px;
  transition: background-color 0.3s ease;
}

/* App Container */
.app {
  width: 100%;
  max-width: 540px;
  margin: 0 auto;
}

/* Header */
.header {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  margin-bottom: 32px;
}

.title {
  font-size: 32px;
  color: var(--text-2);
  font-weight: var(--font-weight);
}

.theme-selector {
  display: flex;
  align-items: flex-end;
  gap: 26px;
}

.theme-label {
  font-size: 12px;
  letter-spacing: 1px;
  color: var(--text-2);
  margin-bottom: 5px;
}

.theme-toggle {
  display: flex;
  flex-direction: column;
  gap: 5px;
}

.theme-options {
  display: flex;
  justify-content: space-around;
  gap: 16px;
}

.theme-number {
  font-size: 12px;
  color: var(--text-2);
  text-align: center;
  min-width: 16px;
}

.theme-switch {
  position: relative;
  background-color: var(--toggle-keypad-bg);
  border-radius: 13px;
  padding: 5px;
  display: flex;
  gap: 4px;
  width: 71px;
  height: 26px;
}

.theme-switch input[type="radio"] {
  position: absolute;
  opacity: 0;
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.theme-switch input[type="radio"]:nth-child(1) {
  left: 5px;
}

.theme-switch input[type="radio"]:nth-child(2) {
  left: 27px;
}

.theme-switch input[type="radio"]:nth-child(3) {
  right: 5px;
}

.theme-indicator {
  position: absolute;
  width: 16px;
  height: 16px;
  background-color: var(--key-bg-2);
  border-radius: 50%;
  transition: transform 0.3s ease;
  top: 5px;
  left: 5px;
}

.theme-switch input[type="radio"]:nth-child(2):checked ~ .theme-indicator {
  transform: translateX(22px);
}

.theme-switch input[type="radio"]:nth-child(3):checked ~ .theme-indicator {
  transform: translateX(44px);
}

.theme-switch input[type="radio"]:focus {
  outline: 2px solid var(--key-bg-2);
  outline-offset: 2px;
}

/* Calculator */
.calculator {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Display */
.display {
  background-color: var(--screen-bg);
  border-radius: 10px;
  padding: 24px;
  text-align: right;
}

.display-input {
  width: 100%;
  background: none;
  border: none;
  color: var(--text-2);
  font-family: var(--font-family);
  font-weight: var(--font-weight);
  font-size: clamp(32px, 8vw, 56px);
  text-align: right;
  outline: none;
  caret-color: transparent;
}

/* Keypad */
.keypad {
  background-color: var(--toggle-keypad-bg);
  border-radius: 10px;
  padding: 24px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 13px;
  grid-template-areas:
    "seven eight nine del"
    "four five six plus"
    "one two three minus"
    "dot zero divide multiply"
    "reset reset equals equals";
}

.key {
  border: none;
  border-radius: 5px;
  font-family: var(--font-family);
  font-weight: var(--font-weight);
  font-size: 32px;
  padding: 11px;
  min-height: 64px;
  cursor: pointer;
  transition: all 0.15s ease;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Key variants */
.key-number {
  background-color: var(--key-bg-3);
  color: var(--text-1);
  box-shadow: 0 4px 0 var(--key-shadow-3);
}

.key-number:hover {
  background-color: hsl(from var(--key-bg-3) h s calc(l + 10%));
}

.key-number:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--key-shadow-3);
}

.key-operator {
  background-color: var(--key-bg-1);
  color: var(--text-2);
  box-shadow: 0 4px 0 var(--key-shadow-1);
}

.key-operator:hover {
  background-color: hsl(from var(--key-bg-1) h s calc(l + 10%));
}

.key-operator:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--key-shadow-1);
}

.key-function {
  background-color: var(--key-bg-1);
  color: var(--text-2);
  box-shadow: 0 4px 0 var(--key-shadow-1);
  font-size: 20px;
}

.key-function:hover {
  background-color: hsl(from var(--key-bg-1) h s calc(l + 10%));
}

.key-function:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--key-shadow-1);
}

.key-reset {
  grid-column: span 2;
}

.key-equals {
  background-color: var(--key-bg-2);
  color: var(--text-2);
  box-shadow: 0 4px 0 var(--key-shadow-2);
  grid-column: span 2;
}

.key-equals:hover {
  background-color: hsl(from var(--key-bg-2) h s calc(l + 10%));
}

.key-equals:active {
  transform: translateY(2px);
  box-shadow: 0 2px 0 var(--key-shadow-2);
}

/* Focus styles for accessibility */
.key:focus {
  outline: 3px solid var(--key-bg-2);
  outline-offset: 2px;
}

/* Attribution */
.attribution {
  margin-top: 32px;
  font-size: 11px;
  text-align: center;
  color: var(--text-2);
}

.attribution a {
  color: var(--key-bg-2);
  text-decoration: none;
}

.attribution a:hover {
  text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 480px) {
  body {
    padding: 16px;
  }

  .header {
    margin-bottom: 24px;
  }

  .title {
    font-size: 28px;
  }

  .calculator {
    gap: 20px;
  }

  .display {
    padding: 20px;
  }

  .display-input {
    font-size: clamp(24px, 6vw, 40px);
  }

  .keypad {
    padding: 20px;
    gap: 11px;
  }

  .key {
    font-size: 28px;
    min-height: 56px;
    padding: 8px;
  }

  .key-function {
    font-size: 16px;
  }
}

@media (max-width: 375px) {
  .keypad {
    gap: 8px;
    padding: 16px;
  }

  .key {
    font-size: 24px;
    min-height: 48px;
  }

  .key-function {
    font-size: 14px;
  }
}

/* Fallback for browsers that don't support hsl(from ...) */
@supports not (color: hsl(from red h s l)) {
  .key-number:hover {
    filter: brightness(1.1);
  }

  .key-operator:hover,
  .key-function:hover {
    filter: brightness(1.2);
  }

  .key-equals:hover {
    filter: brightness(1.1);
  }
}