Hardcore absorption hearts are not visually different enough from normal absorption hearts

The hardcore-signifying markings on absorption hearts in Hardcore mode are extremely light, and almost impossible to notice without really looking hard. they also appear to be asymmetric, as the marking only appears on the left half.

A fixed icons.png that makes the markings more akin to usual hearts is attached. (Although I'd really suggest just splitting up icons.png into its constituent sprites instead.)