wp-spoiler-alert

Installation

1. Click Plugins > Add New in the WordPress admin panel.
2. Search for ”wp-spoiler-alert” and install.

Customization

The Partial and Max blur options control the amount of the blur effect
applied. A value of 0 applies no blur, 20 applies a very large blur
effect, etc.

The Custom option allows you to override the manner in which to hide the
spoilers. This is useful to tune the effect to your site’s theme.

The plugin checks for a custom.css in your current
theme’s directory at {current_theme}/wp-spoiler-alert/custom.css.

If this CSS file is present it will be added to the page automatically.

For eg:- the CSS below makes all spoilers into red blocks.

.spoiler-hidden {
  color: red;
  background: red;
}

.spoiler-hidden:hover {
  color: white;
  background: white;
  outline: 1px solid red;
}

.spoiler-hidden img {
  opacity: 0;
}

.spoiler-visible {
  color: inherit;
  background: inherit;
  outline: none;
}