Restyle the Slides

## Do you have an eye for design?
Help us improve the look of the slide deck.
If you need help, check out the Appendix in the training manual.

The issue names no file or test, so first locate the slide deck in the repository and read the Appendix in the training manual. Clarify the desired visual direction before starting. Done means the slide deck has an agreed, consistently improved visual style.

Written by the indexing model from the issue text.