They likely just use their own engine but it can be made in pretty much anything, even Construct. It's not terribly useful to give a pre-made example. Instead if I can show you how to take any game, and break down what it does in detail you'll be able to make that game.
For example you want to make a game like piano tiles. Well, what does that game do?
One possible description would be: Black squares move down the screen, and when you tap those tiles a note is played. We can do that. With one event we can have a sound play when you tap a tile. One way to make them move down in to to use a movement behavior like "bullet". You just need to set the sprite's angle to 90 so it goes down instead of right (0).
That's simple, but to make it more like piano tiles you need to describe the game better:
A grid of black and white tiles move down the screen. If you tap a black tile a sound is played. You lose if you tap a white tile or if a black tile moves off the bottom of the screen without being tapped.
So we need to figure out how to keep track if a black tile has been tapped, and we need to find out when the tile goes off the bottom of the screen. A variable can be used to keep track if a tile has been tapped.
on sprite touched:
---> play sound
---> sprite: set beenTapped to True
You can compare the y position of the tile to see if it has moved off the bottom of the screen.
sprite y > 480
[inverted] sprite: is beenTapped
---> game over
Anyways you can continue in that manner and make the game more and more complete.