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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
when I useed something like cells[-1][-1],I experted the result is undefined but I got error every time.Here,I learn check the cells[-1]first and then cells[-1][-1],thank you.
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when n ,which is like 13422.129999999 will cause a bug .
yeah,i guess so ,i think him makes joke deliberately，in Chinese ，like "黑"...
Yes,I do.