:root {
  --color-primary: rgb(110, 250, 255);
  --color-secondary: rgb(0, 120, 255);
  --color-accent: rgb(50, 200, 50);
  --color-dark: rgb(90, 90, 90);
  --color-white: white;
  --color-text-primary: purple;
  --color-text-secondary: rgb(100, 250, 250);
  --color-success: greenyellow;
  --color-start: green;
  --color-error: red;

  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;

  --font-family-primary: 'Comic Sans MS', 'Trebuchet MS', cursive, sans-serif;
  --font-family-secondary: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-sm: 1rem;
  --font-size-md: 1.5rem;
  --font-size-lg: 2rem;
  --font-size-xl: 2.5rem;
  --font-size-xxl: 4rem;
  --font-weight-bold: 700;
  --font-weight-bolder: 900;

  --border-radius: 10px;
  --shadow-blue: 0 0 7px var(--color-secondary);
  --shadow-red: 0 0 7px var(--color-error);
  --shadow-inset: inset 0 0 7px var(--color-error);
  --transition-speed: 0.1s ease;

  --button-size-desktop: 75px;
  --button-size-mobile: 45px;
  --button-size-large: 85px;
  --canvas-max-width: 600px;
  --canvas-max-height: 600px;
  --operations-panel-size: 250px;
  --btn-container-height: 250px;
  --btn-container-height-mobile: 95px:
}

.title {
  text-align: center;
  font-size: 2rem;
  font-weight: var(--font-weight-bolder);
  text-shadow: 1px 1px 0 var(--color-text-primary);
  letter-spacing: 2px;
  margin: var(--spacing-md) 0;
}

.game {
  display: flex;
  margin: var(--spacing-sm);
  justify-content: center;
}

.container {
  border-radius: var(--border-radius);
  border: 1px solid var(--color-white);
  position: relative;
  margin: var(--spacing-lg) auto;
  display: flex;
  max-width: 770px;
  justify-content: center;
  align-items: center;
  background-color: var(--color-primary);
  aspect-ratio: 1;
}

canvas {
  margin: 0 auto;
  border: 2px solid var(--color-secondary);
  max-width: var(--canvas-max-width);
  max-height: var(--canvas-max-height);
  background-color: var(--color-primary);
  display: block;
}

.btn-container {
  position: absolute;
  display: flex;
  flex-direction: column;
  justify-content: space-evenly;
  height: var(--btn-container-height);
  background-color: var(--color-secondary);
  border-radius: var(--spacing-xs);
  gap: var(--spacing-xs);
}

.btns-left {
  left: var(--spacing-xs);
}

.btns-right {
  right: var(--spacing-xs);
}

.btn {
  display: flex;
  cursor: pointer;
  font-family: var(--font-family-primary);
  font-family: cursive;
  font-size: var(--font-size-md);
  align-items: center;
  justify-content: center;
  height: var(--button-size-desktop);
  width: var(--button-size-desktop);
  border-radius: var(--border-radius);
  font-weight: var(--font-weight-bold);
  background-color: var(--color-white);
  box-shadow: var(--shadow-blue);
  border: none;
  transition: transform var(--transition-speed);
  flex-shrink: 0;
}

.btn:hover {
  transform: scale(1.1);
}

.btn:active {
  transform: scale(0.95);
}

.btn:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

.operations-container {
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  background-color: var(--color-white);
  height: var(--operations-panel-size);
  width: var(--operations-panel-size);
  border-radius: var(--border-radius);
  padding: var(--spacing-sm);
  position: absolute;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-evenly;
  box-shadow: var(--shadow-blue);
}

.operations-container span {
  text-align: center;
  background-color: var(--color-white);
  font-size: var(--font-size-md);
  font-weight: var(--font-weight-bold);
}

.inputs-container {
  width: 100%;
  display: flex;
  justify-content: space-evenly;
  align-items: center;
  background-color: var(--color-white);
  gap: var(--spacing-xs);
}

.input {
  background: var(--color-dark);
  width: 55px;
  height: 55px;
  border-radius: var(--border-radius);
  color: var(--color-white);
  text-shadow: var(--shadow-red);
  font-size: 1.75rem;
  cursor: pointer;
  font-weight: var(--font-weight-bolder);
  text-align: center;
  border: 2px solid transparent;
  transition: border-color var(--transition-speed);
}

.input:focus-visible {
  outline: none;
  border-color: var(--color-accent);
}

.game-start {
  background-image: url(/imgs/tennis_background.svg), url(/imgs/mathboard4kids_logo.svg);
  background-position: center bottom;
  background-size: 70%;
  background-repeat: no-repeat;
  border-radius: var(--border-radius);
  width: 100%;
  height: 100%;
  background-color: var(--color-text-secondary);
  color: var(--color-text-primary);
  text-shadow: var(--shadow-red);
  display: flex;
  flex-direction: column;
  justify-content: space-evenly;
  align-items: center;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 1;
  font-size: var(--font-size-xxl);
  font-family: var(--font-family-primary);
  font-family: cursive;
  box-shadow: var(--shadow-inset);
  padding: var(--spacing-lg);
}

.start-btn {
  padding: var(--spacing-sm) var(--spacing-md);
  border: none;
  border-radius: var(--border-radius);
  font-size: var(--font-size-xl);
  background-color: var(--color-start);
  color: var(--color-white);
  font-weight: var(--font-weight-bold);
  cursor: pointer;
  transition: transform var(--transition-speed);
  box-shadow: var(--shadow-blue);
}

.start-btn:hover {
  transform: scale(1.1);
}

.start-btn:active {
  transform: scale(0.95);
}

.start-btn:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

.game-over {
  z-index: 1;
  border-radius: var(--border-radius);
  position: absolute;
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
  width: 100%;
  background-color: var(--color-white);
  box-shadow: 12px 15px 30px rgba(0, 0, 0, 0.07);
  padding: var(--spacing-lg);
}

.game-over span {
  background-color: var(--color-white);
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  text-align: center;
}

.restart-btn,
.operation-btn {
  margin: var(--spacing-sm);
  display: flex;
  cursor: pointer;
  border: none;
  border-radius: var(--border-radius);
  padding: var(--spacing-sm) var(--spacing-md);
  align-items: center;
  justify-content: center;
  background-color: var(--color-success);
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-bold);
  box-shadow: var(--shadow-blue);
  transition: transform var(--transition-speed);
  font-family: var(--font-family-secondary);
}

.restart-btn:hover,
.operation-btn:hover {
  transform: scale(1.1);
}

.restart-btn:active,
.operation-btn:active {
  transform: scale(0.95);
}

.restart-btn:focus-visible,
.operation-btn:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

.image-container {
  display: none;
}

@media all and (max-width:768px) {
  :root {
    --font-size-xxl: 2rem;
    --font-size-xl: 1.5rem;
    --button-size-desktop: var(var(--button-size-mobile))
  }


  .game-over span {
    font-size: var(--font-size-sm);
  }

  .game-start {
    font-size: var(--font-size-lg);
  }

  canvas {
    width: 100%;
    height: 100%;
  }

  .restart-btn,
  .operation-btn {
    font-size: var(--font-size-md);
    padding: var(--spacing-xs) var(--spacing-sm);
  }

  .container {
    align-items: flex-end;
  }

  .btn {
    height: var(--button-size-mobile);
    width: var(--button-size-mobile);
    font-size: var(--font-size-sm);
  }

  .btn-container {
    height: var(--btn-container-height-mobile);
  }
}

@media (max-width: 480px) {
  :root {
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
  }

  .title {
    font-size: 1.5rem;
  }

  .operations-container {
    height: auto;
    width: 90%;
    max-width: 280px;
  }
}

@media (prefers-contrast: more) {
  .btn {
    border: 2px solid var(--color-secondary);
  }

  .input {
    border: 2px solid var(--color-white);
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}