Flow Chart Design

This isn’t exactly related to themes or templates… but is about CSS/HTML thus I’m posting it here.

Currently I’m trying to make a flowchart, this is the code I’ve got so far (pasted into a post):

[code moderated - please use the pastebin for any code over the forum limit of ten lines - or post a link to your site]

How can I make only the headings ("step x") for each section be bold and larger? (and not the content after, "blah blah then this etc")

Also, how can I make rounded corners instead of sharp edges?

Thanks!