This app was mentioned in 22 comments, with an average of 3.05 upvotes
Lyne
It's a beautiful puzzler with huge amounts of levels and if you ever beat them all (or get stuck) there's free new levels every day, from easy ones on Monday to increasingly difficult across the week.
No free to play bullshit
https://play.google.com/store/apps/details?id=com.thomasbowker.lynerelease
This question cannot really be answered without info.
If it's for killing time, I recommend going for games instead of just random apps. I doubt you'll kill much time with a note app or terminal emulator.
What kind of games depends on yourself. I usually come back to puzzle games like Lyne when it comes to killing time.
I really like a game called Lyne. It's a join the dots puzzle game with loads of puzzles (it has 26 sets of 25 puzzles with more daily puzzles too). The difficulty curve is very smooth and it's well worth checking out.
I recommend LYNE, it's a minimalist puzzle game with almost no text instructions, and easy to play. The difficulty progresses very fairly and it will keep her brain sharp.
If you reeeally can't afford it there is a blatant copy on the Play Store called Linken. I won't even link that because it's free-to-play with ads, power-ups and lots of IAPs when you can get the full (original!) app for 2€.
I really like LYNE. It's a puzzle game where you have to connect a line from a start to an end (or multiple starts to multiple ends). There are connectors that you can pass through a number of times and things like that, it's very addictive and challenging when you get to about the H set of puzzles from A.
https://play.google.com/store/apps/details?id=com.thomasbowker.lynerelease&hl=en
It's paid but it's very good. Hundreds and hundreds of levels.
I'm a bit irked that Linken is on that list, when it's a completely blatant, IAP plagued ripoff of Lyne.
LYNE - 4.8 rating - $2.99 - Search manually
Paddocks Puzzle - Early Access - $1.99 - Search manually
HEX Editor - 4.2 rating - Free with IAP - Search manually
InBlock - 4.7 rating - Free with IAP - Search manually
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lyne is a fun game for android (link to play store)
it's definitely not the same, but i've enjoyed a game called lyne.
Lyne app is an aeesome game! https://play.google.com/store/apps/details?id=com.thomasbowker.lynerelease
I'm partial to LYNE. Android link.