4x4x4 LED Cube resister problem

Using Arduino LEDs and Multiplexing
1

I am starting to do 4x4x4 LED cube (refer link)

I want to know why there are no resister needed at here.

Is it correct ???

The tutorial using 4 GPIO to control the shared cathode for each layer, using another 16 GPIO to control the anode.
There are nothing and directly connect these 20 Pin to D0-D13 & A0-A5.
I am using a this color LED, seems need ~3.3v

2

Is it add 4x S8050 between shared cathode and A2-A5 ??

3

I want to know why there are no resister needed at here

Because “The designer“ is an idiot.

4

Current limit resistors should be used. If not, the shared cathode pins are being tasked to absorb a lot of current and will burn out.

5

No resistors would be needed if driver chips with constant current outputs were used. Arduino pins are not constant current.

6

No mention of that made in the referenced link tho.

7