The HTML/JavaScript code here imitates the eye-catches, or commercial bumpers, from “Miss Kobayashi's Dragon Main” (『小林さんちのメイドラゴン』). The example below is from the 5th Episode.
All the eye-catch shots consist of 5 letters, displayed one by one at a short interval (roughly 600 ms) with clicking sounds, on a plain yellow background. The letters hint somethig, most likely, related to the episode. For example, the 5th episode depicts Kobayashi-san at work (she is a Pythonista), hence something related to programming.
The code was originally posted to Qiita. Click here to see the code in action.