The longest titled game/app I've ever encountered, this is - quite literally - painting by numbers, as the title suggests. So if you're doing it properly then you're zooming in to each picture, selecting each shade or colour from the numbered pallette and then tapping to daub virtual paint in the appropriate cells. Yes, it's tedious in the extreme for an adult, but this may just be a creative hit with your kids - it'll certainly help them while away a few hours, perhaps on a car journey?

From the Store description:

Kids and adults love to color by numbers and we have got a lot of things for you to choose. Color by number pages are a great way to teach your kids or students basic number recognition, how to use a legend and it will give them the opportunity to work on their fine motor skills. Enjoy the coloring book with your creative ideas and feel yourself as an artist with a complete variety of anti stress pictures.

• Just paint by numbers in this interesting sandbox game.
• Color drop in the same numbers blocks.
• That you will finished a cool pixel works.
• Just follow the numbers in pictures and make an amazing drawing.

• Perfectly develops children fine motor skills
• Paint easily any image.
• Share with friends on Instagram, Twitter or Facebook Messenger
• Family-friendly content: coloring anti-stress pictures suits for both adults & kids
• Perfect relaxing way to become the master of your own mind.
• Many interesting pages for you to color.

Trains your concentration and steadiness Or just want to color your own way, practice your drawing and coloring skill. This is a great activity to practice your drawing skills. It’s also fun for any age to try to finish the drawing.

Here's 'Pixel Art - Sandbox Number Coloring Book - Color by Number UWP' (phew) in action:

Each pack (you get one for free) has over a dozen detailed 'numbered' designs. Once on screen, you can zoom in to see the pixel details and which numbered brush you need for each...

It's then a matter of 'painting', in this case tapping on each pixel with the appropriate numbered brush selected. Fluent and enjoyable it's not - at least not for an adult, I contend! If you want to 'become master of your own mind' then learn a new language or take up programming or, well, anything! (right) five more picture packs are available, 79p each, plus there's an extra IAP to remove the annoying banner ads. All fair enough, especially if your kids really get the hang of this type of artwork.

You can grab this in the Store here.