Table 2.

Suggested changes to the digital intervention materials that were categorized by the research team as Must have and subsequently implemented.

Suggested change during interview	Changes made to the digital intervention materials
Add that intrusive memories come without warning or are involuntary somewhere in the video	Changed the summary sentence at the end of the video from “pop up in your mind without warning” to “pop suddenly into your mind when you don’t want them to” to emphasize that they are involuntary
Clarify the distinction between rumination and intrusive memories, by adding examples of the former, such as thinking “what could I have done differently?” or “why did this happen to me?”	Added to the script for the video on intrusive memories, “they are also NOT the same as thinking in words, like ‘Something awful happened to me’”
Clarify the three red drops of blood image, perhaps by drawing a red puddle instead, as it was difficult to distinguish what this was	Animation in the video was altered to represent blood more clearly
Emphasize mental rotation more as it is thought to be critical to the intervention’s efficacy	Changed the script and rerecorded to say, “for this intervention to work, the most important thing for you to do is focus on the blocks that are coming up next”
Annunciate the word brain more clearly and others a little clearer	Both videos have both been revoiced by a different person, with emphasis on clear annunciation
Say in the video that this is playing Tetris with special instructions	Change the name of the video when it is presented to target users to “Tetris with Special Instructions”
For the “How to Play Tetris” quiz, the first question, two of the possible answers are technically correct	Changed the first alternative for the first question from “Score as many points as possible” to “Getting as many orange blocks as possible” so that latter is more clearly incorrect
Some phrasing from the video is not included in the “How to Play Tetris” quiz, like saying “planning in your mind’s eye”	Changed the first option of the last question from “Visualise and rotate them in your head” to “Visualise and rotate them in your mind’s eye”
The wording of one question in the “What Are Intrusive Memories?” quiz, where the one option says, “intrusive memories usually take the form of...” “a headache” can be true for some participants and should be changed	Changed the third option of the second question stating that intrusive memories usually take the form of “a really high fever” to be more clearly incorrect