Sparks Cry of Mercy does a really nice job carrying its song's energy, and has a more raw, unrefined edge that I think works very well with the very messy song that's used. A lot of the block designs are semi-transparent, which historically tends to mean muddy details and a lack of "solidness" to the structures, but two choices were made that I think help the designs out drastically; the consistent use of black "outline" sections, and the general bright colours and subtle details used in the semi-transparent sections. The darker outline portions contrast very nicely with the rest of the level and helps the structures stand out, and the usage of glow and the line-based designs help both break up the large chunks of flat black as well as to add more texture and detail to the designs. The interior semi-transparent portions themselves all have some sort of subtle detailing, similar to reflections bouncing off of glass, and are coloured brightly enough that they aren't muddied too much by the rest of the level and serve to accent it instead.

I also think the less polished nature of the level works in its favour in regards to the gameplay. The structures are all very simple, and there tends to be a lot of negative space between them (most noticeable around 0:49) that relies on the background as filler, but Sparks Cry of Mercy has such fast-paced gameplay and bright colours that I think attempting to remedy these issues would have drastically lowered the gameplay clarity. The simple shapes and excess of negative space combined with the aforementioned contrasting block designs all help the player easily intuit exactly where the gameplay is and what will and will not kill them, which in my opinion is a necessity for fast, high-CPS gameplay and contributes to an overall excellent playing experience for this level. The lack of heavy shaders or camera controls further solidifies the level's already good readability, which is a nice bonus.

Some individual parts do make an effort to stand out - there's a fake 3-way "dual" at 0:51, a dash orb that breaks through one of the structures at 1:13, and some other nice novelties that are very cool additions in their own right - but overall I think the level does get monotonous. The colour scheme stays the same aside from the red in the first part, the structuring and design styles are the same, even the background structures are reused fairly consistently. While cohesive, I'd love to have seen some more usage of slopes, or another spin on the outline sections of the structures, or even a different mechanical/electronic style altogether for some of the more intense parts. However, I'd consider this a relatively minor issue, and overall really enjoy Sparks Cry of Mercy. I will be keeping an eye on ISGAgaru's levels going forward and look forward to more from them.