The traditional board game Triominos really needs no introduction.
Maikel Dijkhuizen

Try to get rid of all your triangular tiles by placing them against triangles with corresponding numbers. The trick here is to score as many points as possible.
Notably, you can only play this app in landscape mode. Due to the spacious playing field, a smartphone screen is a bit on the tight side. It is therefore preferable to use a tablet.
A nice extra is that you can play online against friends or strangers. This does require an account, by the way. Alternatively, you can also compete against computer-controlled opponents. Choose Easy, Normal or Hard as the game level, after which the playing field opens. At the bottom of the screen are all your triangles. Try to place a stone or take a new one from the pile. In the latter case, you will receive minus points. The operation is simple. Swipe a pebble to the desired spot. The triangle rotates automatically in the right direction if necessary. Don’t see a solution? Then ask for a hint.
A disadvantage is that commercials appear at different times. For an amount of a few euros you can hide this advertisement.
Triominos
Price: free
System requirements: Android 4.1+, iOS 10.0+
Language: Dutch