The blog is now out for a month, I started to think about promotion. I created a twitter account (@umlgameprog), and start to put links on hackernews. It immediately raised the number of visitors to about 150 per day! This count is computed by WP Statistics plugin, I don't know if it is good, maybe I should try Google analytics.
I also installed Yoast SEO Wordpress plugin. It gives me some advice on my posts (missing image alt, focus phrase, ...). I try to follow them the best I can !!