I really like to play from time to time a short game online. When I want to take a short break I go to Gameszap and play the best games. I like the design and the colors, I like that on mobile I know from the start which games are mobile-friendly or not.
They have a big variety of online games, from those for kids to those for grandparents like Candy Crush. Another good facility of the site is to save each game on your pc/laptop/smartphone - so the next time you want to play it, just click a shortcut.
Here I found a big collection of old Flash games - which is really nice to have.