"Piercing blue eyes" Who thinks that? Who says that? Who reports that? Who experiences that visual sensation? Author, narrator, or viewpoint character? Narrated or nonnarrated narrative? Overt narrator or covert narrator? I'm going into intermediate writing "mistakes" though, which "rookies" might also make. The issue I see is unsettled voice, when a narrative shifts awkwardly from a lecturing-from-a-stage author commentary to narrator observation to narrator reported viewpoint character perception and cognition and back and forth without a meaningful rhetorical purpose.
"Piercing blues eyes" is unequivocally Description. It could also be Introspection if thought by a viewpoint character, probably not Action, least likely to be dynamic action, also can be Narration, maybe somewhat Emotion, a visual Sensation, maybe a tactile sensation, unquestionably a Summarization, most descriptions logically can only summarize, also possibly Exposition information detailing, if in dialogue then it is Conversation, might be a Recollection, not likely Explanation but not unequivocally, unlikely to be Transition. DIANE'S SECRET.
To me, "piercing blue eyes" works best when it's reported as a viewpoint character's perception or cognition, less effective as a narrator's perception. The narrator is making a judgment call, telling and summarizing for readers how the eyes are meant to appear from the narrator's subjective perspective. Weakest if author's surrogacy transparently is involved. Context matters most. Anything might work if it's closest to a viewpoint character's perceptions and cognitions.
Flat characters aren't necessarily poorly portrayed characters. Flat mostly means a character who's superficially depicted, might be solely physically described. A character whose physical appearances are amply depicted can still be flat. A character who's not abundantly appearance-wise described can be round if personality and behavior traits are portrayed. In other words depicted with a depth of personality. Flat characters artfully take a backseat in narratives with setting, idea, or event emphasis. A round character is one who audience readers have a close personal rapport with because of similar personality traits, emotions, behaviors, values, needs, and/or desires, to the point readers become the character, and without jeopardizing rapport by a central character having a markedly different physical appearance than readers.
Kurt Vonnegut's "Harrison Bergeron" has all flat and static characters. It's an idea, event, and setting time, place, and situation short story populated with MacGuffin personas. Melville's "Bartleby the Scrivener" has all flat characters. Bartleby is peculiarly dynamic in his static nature though. Isabella Swan is not amply, physically described, nor is she flat or static. Twilight readers get to be closer to Bella because they can become her without a pesky dissonance of appearances.
"Harrison Bergeron" 1961, 2,000 words.
http://www.tnellen.com/cybereng/harrison.html
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