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.

Locate the slide deck in the repository and review the Appendix in the training manual for context. Compare the current slides with the requested improvement to their look; the work is complete when the deck has a consistent, improved visual design.

索引モデルが issue の本文から書いたものです。