Arranging the images in the sprite horizontally as opposed to vertically usually results in a smaller file size.
Combining similar colors in a sprite helps you keep the color count low, ideally under 256 colors so to fit in a PNG8.
"Be mobile-friendly" and don't leave big gaps between the images in a sprite. This doesn't affect the file size as much
but requires less memory for the user agent to decompress the image into a pixel map.
100x100 image is 10 thousand pixels, where 1000x1000 is 1 million pixels
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