- [X] friction (default: .5)
- [X] expected number of contacts (default: 1)
- [X] save modifications in the json file
-- [ ] new item
+- [X] new item
+ - [X] create the item
+ - [X] refactor: single list of items in the json
+ - [X] save the new item in the json
+ - [X] delete item
+ - [X] id
+ - [X] strategy and strategy_args
+ - [X] pop up if errors with arguments in strategy_args
- [ ] new scene
- [ ] start items
- [ ] editing of test_items in the editor for functional tests