Nice puzzle game!

It reminds me of Lines X for Nintendo Switch that I really enjoy. [1]

For me, I would have preferred even less text than currently in the tutorial. If you look at the image on the first Lines X page I link below of the two turquoise dots, that's the first page of that tutorial. No text at all. You have to connect the two dots by swiping. The next tutorial screen has some extra black dots, and you learn that you have to cover all black dots with your line as well, not only connect the colored dots. Though I have to say, my mother couldn't figure that step out in Lines X without my help, even when she's into different types of puzzles, so it can be argued that having no text will only appeal to more hardcore users.

But something similar could be done in your game. I didn't need the text in the first tutorial screen, because the 4
and the empty squares would make me swipe to see what happens, and I can at a maximum cover 4 squares in any direction. Also, the line changes color when you reach the correct number of squares, which is plenty information that this is the intended length. On the second screen, I don't need text to tell me lines can't overlap, because the tutorial won't advance until I create the correct solution.

I would allow a bit more trial and error from the user instead of explanatory text. The minimalism can be taken further. That way you can learn the game and figure out the rules at the same time.

Here are some suggestions, that you can use if you wish:

1. Hide the text in the tutorial by adding the text "help" next to "quit" in the bottoma of the UI, or a question mark somewhere. The first tutorial page should (according to me) just be the puzzle! Clicking help would show the text and the heading "Welcome to Ordinary Puzzle" and so on, and clicking help again would hide all text from the page.

2. Consider showing currently solved and the maximum number of puzzles of each size. For example:

small 3/100

medium 0/100

large 0/100

That way the player gets an estimation of how large the game is, and it might encourage players to finish more puzzles. Or if the number of puzzles are automatically generated and infinite in number, a would like to know how many I've finished of each size.

3. Clicking the number and stars in the top right should lead to a progress page or at least an explanation of stars. Currently I don't know what "38" means after solving a couple of puzzles. It would make more sense to me if it said the number of finished puzzles, but right now I don't know what the number means. Total number of squares with lines in finished puzzles? I just finished a new puzzle and it says "+27", but I don't know what the 27 stars are from.

4. After finishing a puzzle, I don't need the screen that shows the puzzle name and having to click "new puzzle". I'd like the game to automatically start the next puzzle, possible after showing the puzzle name and "completed", which would make me finish more of them in succession. If I want to stop playing, I can click quit from the next puzzle, I don't need to be asked between every puzzle.

5. I agree with the other poster who wanted to start from any square, where the line would be tossed if it doesn't connect to a number. On the other hand, I can definitely view the current implementation as a slight quirk of the game, and accept the way it works. It doesn't take much away from the game the way it is, and it reinforces that you have to interact with the numbers in some way and not just swipe randomly. So having the numbers start each interaction makes sense from that perspective.

[1]

https://www.nintendo.com/games/detail/lines-x-switch/

https://www.nintendolife.com/news/2019/06/lines_x_is_a_relax...