The way I've found which works well (and which I try to stick to) is to take it in stages. Work on a large grid size to begin with, get the main layout done. Then work your way down, adding smaller and smaller details, until you're there.
Try and draw out a plan on paper, it really helps.
A random idea from me is something that randomly occured to me:
Ladder racing! You go faster on ladders in css, so why not use ladders on tracks and have players 'race' against each other on them.
Not really proper CSS, but, well, it seemed like it might be 'fun.'
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