There's a game where you have to spot the smiling face amongst the neutral and scowling faces.
To begin with, especially if you are feeling very negative, you may be quite slow to spot the one smile amongst the scowls and blanks. However, you can practice and you'll soon find you are spotting the smiles more quickly. This is exactly what goes on when you are in an optimistic frame of mind - you focus on the positive and discount the negative.
If you are interested, you can click on this link. You'll just have to add your email address plus your name and year of birth (which are used for some of the games). The smile game is called Matrix. And it's all free (although you can pay a subscription if you want to save your scores).
The site will open in a new window so the Chill Out Course will still be behind it.
Try the Matrix game on MindHabits