once-campfire/app/assets/stylesheets/buttons.css

:root {
  --btn-size: 2.65em;
}

.btn {
  align-items: center;
  background-color: var(--btn-background, var(--color-text-reversed));
  border-radius: var(--btn-border-radius, 2em);
  border: var(--btn-border-size, 1px) solid var(--btn-border-color, var(--color-border-darker));
  color: var(--btn-color, var(--color-text));
  cursor: pointer;
  display: inline-flex;
  font-weight: 600;
  gap: 0.5em;
  justify-content: center;
  padding: var(--btn-padding, 0.5em 1.1em);
  pointer-events: auto;
  text-align: center;

  img {
    -webkit-touch-callout: none;
    user-select: none;
  }

  /* Default icon styles */
  &:where(:has(img):not(.avatar)) {
    text-align: start;

    img {
      inline-size: 1.3em;
      max-inline-size: unset;
    }

    img:not([class]) {
      filter: invert(0);

      @media (prefers-color-scheme: dark) {
        filter: invert(100%);
      }
    }
  }

  /* Circle buttons */
  &:where(:has(.for-screen-reader):has(img, figure)) {
    --btn-border-radius: 50%;
    --btn-padding: 0;

    aspect-ratio: 1;
    block-size: var(--btn-size);
    display: grid;
    inline-size: var(--btn-size);
    place-items: center;

    > * {
      grid-area: 1/1;
    }
  }

  &:where(.avatar) {
    --btn-border-radius: var(--avatar-border-radius);
    --btn-padding: 0;
    --btn-border-size: 0;
    --hover-size: 0;

    justify-content: unset;

    img {
      inline-size: 100%;
    }

    @media (any-hover: hover) {
      &:where(:not(:active):hover) {
        filter: brightness(0.7);
      }
    }
  }

  &:where(summary) {
    list-style: none;

    &::marker,
    &::-webkit-details-marker { display: none; }
  }

  img {
    user-select: none;
    -webkit-touch-callout: none;
  }

  [aria-busy] &:disabled {
    position: relative;

    > * {
      visibility: hidden;
    }

    &::after {
      --mask: no-repeat radial-gradient(#000 68%,#0000 71%);
      --size: 1.25em;

      -webkit-mask: var(--mask), var(--mask), var(--mask);
      -webkit-mask-size: 28% 45%;
      animation: submitting 1s infinite linear;
      aspect-ratio: 8/5;
      background: currentColor;
      content: "";
      inline-size: var(--size);
      inset: 50%;
      margin-block: calc((var(--size) / 3) * -1);
      margin-inline: calc((var(--size) / 2) * -1);
      position: absolute;
    }
  }

  &:has(input:checked) {
    --btn-background: var(--color-text);
    --btn-color: var(--color-text-reversed);

    img {
      filter: invert(100%);
    }

    @media (prefers-color-scheme: dark) {
      img {
        filter: invert(0);
      }
    }
  }

  &:has(input[type=checkbox][disabled]) {
    cursor: not-allowed;
    filter: grayscale(100%) contrast(0.5);
    opacity: 0.5;
    pointer-events: none;
  }

  [disabled] &[type=submit],
  &[type=submit]:disabled {
    cursor: not-allowed;
    filter: grayscale(100%) contrast(0.5);
    opacity: 0.5;
    pointer-events: none;
  }
}

/* Variants */
.btn--reversed {
  --btn-background: var(--color-text);
  --btn-color: var(--color-text-reversed);
}

.btn--negative {
  --btn-background: var(--color-negative);
  --btn-color: var(--color-text-reversed);
}

.btn--reversed,
.btn--negative {
  --btn-border-color: transparent;
  --hover-size: 0;
  --hover-filter: brightness(0.7);

  img:not(.avatar) {
    filter: invert(100%);

    @media (prefers-color-scheme: dark) {
      filter: invert(0%);
    }
  }
}

.btn--success {
  animation: success 1s ease-out;

  img {
    animation: zoom-fade 300ms ease-out;
  }
}

.btn--faux {
  --hover-filter: none;

  box-shadow: none;
  cursor: initial;
  outline: 0;
}

.btn--borderless {
  --btn-border-color: transparent;
}

.btn--plain {
  --btn-background: transparent;
  --btn-border-color: transparent;
  --btn-padding: 0;
}

.btn--pulsing {
  animation: pulsing-outline 2s infinite both;
  outline: 0 solid var(--color-alert);
}

button {
  @media (any-hover: hover) {
    cursor: pointer;
  }
}