Once microtransactions are up, you will also probably be able to buy cards you don't have.
That's probably when challenges are going to go back to one a week.
Don't quit your day job.
Also, (and this is good advice for any developer), don't use a completely unrelated image for your game's icon. Seriously, it's incredibly misleading when you have an icon showing a 3D rendered action image and the game graphics were drawn in Paint.
Decent for a first game. No apparent bugs, everything is responsive and works well.
My only comment is that I would like to see an "infinite mode" - where you keep going until you lose, with the pieces coming faster and faster, rather than the current level-based system.
Well done.
Random is random. Runs of bad luck happen.
4 levels is really an insignificant amount - unless you mean four areas.
Some terrains give a bonus to a certain magic power - in those areas, you can use that magic at level 1 even if you have no creatures of that type.
Beast Magic is overpowered.
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