No gradient effect (strange) when font_size = 70

[yasenstar]

Hello all,

I'm learning "Using Gradients" from Tutorials & Guides pages.

The font_size in sample is set as 96, which is working fine both online (docker contrainer) and my local environment (Windows, VS Code).

But, when I set the font_size=70 in my local, the gradient effect is not shown, see below screenshot I highlight in the left part, however, the online docker running still OK:

Below I'm putting the interesting testing showing font_size from 68 till 72, looks like only 70 is the special one with no gradient can apply:

Is there any hints why it's like this? Thanks a lot.
Xiaoqi

[yasenstar]

My testing code is in this repository:
https://github.com/yasenstar/python/tree/master/Manim/2_Thematic/2.3_Text-Formula/1_text_without_LaTeX/2.3_1_08-1