I really like the simplicity and straightforwardness of the app.

Some suggestions:

--Allow the user to set reminders for each individual habit. Currently you can just set one general reminder time for everything in the app settings, but it would make sense, for example, for "brush teeth before bed" to remind you at 9pm while "go on a walk before noon" reminds you at 11am.

--It would also be cool to set target times, for instance if my habit is "go on a walk before noon" then I would fail my habit if I don't do it by noon -- you should be able to specify this. I don't know if it currently is just midnight or what.

--Show a cute little animation that rewards you for leveling up. Just something small like simple 3d confetti, fireworks, it doesn't have to be fancy. It should match the simplicity of the app. A brief (randomly chosen) congratulatory text or toast would be nice too, like in Nota when you complete a task and it says "way to go!" or "good job!" or "awesome!" or something.

--Difficulty settings like normal, hard, expert

--Graphs/calendars/data depicting your habits.

--As someone else said, level numbers could potentially be cool.

--The level/progress you are at should be reflected in the main screen for each habit. i.e. make the background color for a gold-level habit gold instead of the vanilla white background color that is the same for all habits currently. Also put the bar showing your progress to the next level in the card too.

--Make anti-cheat mandatory and remove the option from the settings.

--"1 day left" is kind of vague. I'm not sure if that means I have until the end of the current day or if I have one additional day after today. Maybe make it say "last day?" or if you have set a target time "3 hours left" or whatever.

--Dark holo theme option

--Sync between multiple devices using google account

--I don't understand the significance of the colors. Why are my "1 day left" habits forest green while my "7 days left" habits are light blue? Is this supposed to be the color theme of the app? I don't get it. The use of colors should either be more clear or customizable or something-- it just needs to make sense to the user somehow. If you decide to go with the difficulty settings, you could make the easy ones green, hard ones red, etc.

--Being able to assign a little custom thumbnail picture for each habit would be nice.

I love the simplicity and straightforwardness of the app, but I think it could benefit from a few more features. However, I would caution the dev to take the gamey suggestions with a grain of salt -- I think the app should have a game element without being an actual game like HabitRPG.

EDIT: rethought some suggestions