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 does not name the slide-deck file, its entry point, or any tests. Start by locating the slide deck in the repository and review the Appendix in the training manual for context. Before changing anything, clarify which visual problems and acceptance criteria define a completed restyle.

Written by the indexing model from the issue text.