<opinion> I've tried CodinGame for a brief while, but became less enthusiastic of using it because of the fantasy/RPG/war game theme. Personally, the visuals, the (sometimes slow) execution of the code because of the animation, and the gaming references (descriptions) distracted me from actual coding and learning.<p>Codewars (except for the name) has less emphasis on the in-game competition and fight. Although that visual theme is also rather dark, there's less distraction.<p>Personally, I'd prefer even a much 'cleaner' UX and UI. Or -- but with loss of the advantages (but also disadvantages) of coding in the browser window -- code challenges that just require a number or string to be submitted as an answer. (Project Euler, Advent of Code, Google Code Jam.) Then my whole coding environment is under my control, and the programming languages and tools to be used aren't restricted as well by the platform provided.<p>But having said that, CodinGame looks great (if you fancy the theme) and is really well executed. It's just not my cup of tea.
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