Yeah, the Web version is a bit undertested (right now the main menu looks janky if not displayed in full screen). For teleporting bosses some (albeit- very few) possible teleportation positions can fall too close to the camera. I'll try to fix those issues before the end.
As for the second boss- tanks for rising this! Personally I didn't see it as an issue, because both the player and to boss move around a lot during this fight, and even if the player is covered for a moment he usually soon moves to a visible position. The silhouette that's visible is a great idea, but seems like a bigger fix (or at least longer to test out proper), and TBH I don't know if I'll have the time right now (personal stuff- that's why I'm uploading early :))
Anyway- glad you liked it, and thanks for the feedback!