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* NEW: Added support for stepping back in time during debugging (Run => Step back) by Alar Leemet. If you accidentally stepped over an interesting part of code, then now you can step back and step into.
* NEW: Added support for UI and syntax theming (https://bitbucket.org/plas/thonny/wiki/Theming)
* NEW: Added several built-in dark themes
* NEW: Added support for display scaling / high-DPI screens (Tools => Options => General)
* NEW: Added closing buttons to the tabs of all views
* NEW: Added support for (CPython) back-end plug-ins (https://bitbucket.org/plas/thonny/wiki/Plugins)
* NEW: Current editor line can be highlighted (Tools => Options => Editor)
* NEW: Thonny can be started in simple mode (https://bitbucket.org/plas/thonny/wiki/Modes)
* NEW: Variables view now allows viewing variables from other modules beside __main__ (Tools => Options => General)
* CHANGED: Dropped support for Python 3.4 (both for front-end and back-end)
* CHANGED: Reorganized back-end configuration ("Tools => Options => Back-end" instead of "Tools => Options => Interpreter")
* CHANGED: The roles of Interrupt and Stop commands are now more clear: Stop always restarts the backend and Interrupt only tries to interrupt
* CHANGED: Editing the running program doesn't interrupt it anymore.
* CHANGED: Object inspector now shows attributes and object overview on different tabs
* CHANGED: Can't set thonny.THONNY_USER_DIR directly in customize.py anymore (https://bitbucket.org/plas/thonny/wiki/DeploymentOptions)
* CHANGED: For plug-in writers: Unified early and late plug-ins (load_early_plugin should be renamed to load_plugin)
* CHANGED: For plug-in writers: get_workbench and get_runner moved from thonny.globals to thonny
* FIXED 358: Hide the stacktrace of SystemExit
* FIXED 368: "Open system shell" doesn't work in Xfce (fix by Miro Hrončok)
* FIXED 370: Made zooming with Ctrl++ / Ctrl+- work on the numpad on Linux
* FIXED 372: Now it's possible to specify a link as backend interpreter (fix by Miro Hrončok)
* FIXED 396: exec causes range marker to crash
* FIXED 403: Window width may become negative
* TECHNICAL: Changed the location and sharing of backend.py, common.py, ast_utils.py
* TECHNICAL: Cleaner approach for sharing jedi with the back-end
* TECHNICAL: Package manager now uses pypi.org instead of pypi.python.org
* TECHNICAL: Several changes in Runner and BackendProxy interface
* TECHNICAL: Saving an editor now forces writing to disk (see https://learn.adafruit.com/adafruit-circuit-playground-express/creating-and-editing-code#1-use-an-editor-that-writes-out-the-file-completely-when-you-save-it)