I like the website but don’t find the animation intuitive, sorry! I always position (for Ax = b) the A matrix with the x matrix to the top right of it. To the right of the A matrix, under the x matrix, I draw the resulting b matrix. I then draw a line through the (1,1) position of x downwards to b. It hits (1,1) of b, then I do the same horizontally from A(1,1). I take the dot product of the numbers which the two lines intersect, and repeat for all other positions. This is the only way I can remember matrix multiplication! It made my life so much easier and I am always on the lookout for intuitive visual tools for mathematics concepts. I don’t know if this is a really common tool, it was taught to me by my university professor Burkard Polster (the Mathologer on YouTube).