If you are Roman Catholic, then the only things you will be held accountable for under penalty of mortal sin are the fast requirements on Ash Wednesday and Good Friday and also the abstinance of meat on other Fridays in Lent.
Everything else is a personal choice that you are free to modify if you so please. However, please do remember the reasons for the initial sacrifice.
Some people give up something for all of Lent, Sundays included
Some people allow themselves the item on Sundays.
There is no rule that you have to do either.
Personally, I now follow the allow myself the item on Sunday rule, but this is only because I found out about this allowance a few years ago during a retreat with my Newman Center that was during Lent. I indulged in the item I gave up then that Sunday and I generally have done so ever since for items I give up.
When I was a teen I played video games regularly and I think I tried giving it up once. I did not know about the Sunday rule and when I bought a new game that I had been loooking forward to coming out for several months, I had friends play it just so I could at least see what it was like, while waiting those last few days (It came out during Holy Week)
My point is that there are no rules for this except your own so that you can grow spiritually. Sometimes I give in and I realize just how spiritually weak I am when I can’t even go so many days without something. And I will make all sorts of rationalizations of why it alright to do something that I originally planned on giving up but it it still a rationalization.