Directly quoted:

https://www.gamedeveloper.com/design/interview-storytelling-through-narration-in-i-bastion-i-  (Bastion as inspired by the American Frontier AND the bit about representing the sky)

https://web.archive.org/web/20110509073057/http://www.gamasutra.com/view/news/33156/Road_To_The_IGF_Supergiant_Games_Dynamically_Narrated_Bastion.php   (Bastion's art style)

https://gameinformer.com/2021/05/20/the-story-behind-supergiant-games-transistor  (restarting Transistor development)

Whitford, Frank (1990). Klimt. London: Thames and Hudson (referring to Klimt's eyes as Egyptian).

Sampled briefly from:

Giantbomb's Building the Bastion - https://www.youtube.com/watch?v=r_pxalQeLpM
[NoClip's] The Making of Bastion - Documentary - https://www.youtube.com/watch?v=uo7TcJ2E0-I
[NoClip's] The Untold Story Behind the Design of Transistor - https://www.youtube.com/watch?v=SL2Pk2jP_6s

Thanks to NoClip for getting Supergiant to post their concept art:
https://imgur.com/a/concept-arts-screenshots-of-pyre-from-making-of-pyre-documentary-lmvS2Dp?grid

Informative Recommendations (which aren't sampled in the video):
Skyehoppers' Bastion video - https://www.youtube.com/watch?v=X4VdAg70dU8   for the strongest take on Bastion
https://www.pointnthink.fr/en/the-art-of-hades-en/   for discussion of Hades' art direction
https://videogamearchitecture.wordpress.com/2016/06/13/transistor-the-art-nouveau-influence-on-cloudbank/  on Transistor's art direction