NBack 3D

The task is only to count the 3D shapes of the specified shape and color, but as the N of the N ‘Back increases, it becomes more difficult.
*N’Back : The current answer matches the one from N steps earlier in the sequence.
*1’Back
1 task1: count & memorize
2 task2: count & memorize
3 answer for task1
4 task3: count & memorize
5 answer for task2
6 task4: count & memorize
:
*2’Back
1 task1: count & memorize
2 task2: count & memorize
3 task3: count & memorize
4 answer for task1
5 task4: count & memorize
6 answer for task2
7 task5: count & memorize
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