Im really glad you liked it, i started with a Lydian melody for the "brightness" (using Melodic minor #4 for a twist) and then i just say "well, i think in a journey you are suposed to move" so in the nexts parts i started mixing all that i know about functional harmony(secondary dominants,tritone substitution) , cubedance(neo riemannian theory) and for the D part a little bit of bartok axis (the Fm7 |A |C |Dmaj7 that is apparently absolutly outside of the G# minor implied by the G#m |A7 |A#m |B at the end), always with the intent of finishing the part on a chord that was "close" to the one coming next.
What con i say about the metal memes? the only thing i can say is that im a big sucker for the actual prog/tech death scene and maybe i didnt incorporate the insane riffing of those bois, but they always use tasty harmonies and sick bass lines.
Cheers