Front Page Design Updates

[cycomachead]

I think we can make the front page feel a little easier to use.

• only show at most 3 buttons, not 5.
• We shouldn't link to the PDF reference manual
• Consider reducing the spacing around the banner?
• Snap! banner backgrounds should be white?
• carousels should show 6 projects and reflow to 2x3 on very small screens.
• Should small screen carousels only show prev/next controls, and not first/last? (2 buttons vs 4) Should they be larger?
• Should we show alonzo saying welcome? There is no alonzo anywhere....