In my series of game engines evaluating and experiment, Godot comes as a very first candidate by following reasons.
Pro
- Godot is open source: you can find it here: Github
- Document is well written and easy to learn. Link
- Supports both 2D and 3D games, and not (3–1)D like Unity :D
- GDScript (Godot script) is Python inspired with Lua performance and Python syntax, it helps your scripting more readable and organization
- Scene/UI editor: it helps designers and developers work with same tool and share the same work flow.
Cons
- Lack of official 3rd party modules such as In-App-Purchase, Analytics or Ads. If you need them, search on Github or create yourself
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