Upvote:1
In general, the best way to find out what the catechism teaches is to read it.
Here's a link to the catechism article on the Third Commandment.
I would add to this as an addendum a simple truth; in practice is not the same thing as in truth. We are all sinners and we all fail, and fail often.
You shouldn't really be doing any gainful work on a Sunday unless necessary. CCC 2185 specifies that family needs and important social service can legitimately excuse someone from the Sunday obligation, but this should not be allowed to lead to habits "prejudicial to religion, family life and help".
CCC 2186 informs the faithful to be mindful of those who cannot take rest from work due to "poverty and misery".
In brief, as stated by CCC 2194, the day should be geared towards the cultivation of the faithful's "familial, cultural, social and religious lives". Worship should be offered to the Lord, time spent with family and friends, and rest taken. Works of mercy are appropriate and good on the Lord's day.
One shouldn't use the free time for things like household chores, errands or gainful employment. Hobby projects and the like are generally acceptable; writing, pottery, art, coding, whatever floats your boat as long as it doesn't subvert the proper purposes of the Lord's day.