Design a high-fidelity desktop web UI mockup, 16:10, rendered as a flat screenshot -- no browser chrome, no laptop frame, no hands, no desk, no perspective.

Brand: Subnaut. A developer tool. Tone: precise, quiet, engineered. Not playful, no gradients, no glow, no 3D, no stock-photo people, no purple-blue SaaS look.

Palette, used exactly:
  background   #ffffff
  raised panel #fbfbfa
  primary text #0a0a0a
  body text    #46464a
  muted text   #8a8a90
  hairline     #e8e8e6
  accent       #12a37a  (a restrained green -- use sparingly, for one action only)

Type: a clean grotesque sans (Inter/Helvetica feel) for prose. A monospace face for labels, eyebrows, code and buttons -- uppercase, wide letter-spacing, small.

Layout: generous whitespace, a strict 12-column grid, thin 1px hairline rules as the main separator instead of borders or shadows. Left-aligned. Flat.

Mood reference: the Bittensor site, Linear's docs, Stripe's density -- engineering documentation, not a marketing splash.

Page: sign in. A single centred card, about 400px wide, on a plain white field -- nothing else on the page.

Card, top to bottom: a small circular node mark beside the wordmark; a heading "Sign in"; one muted supporting line; an email field; a password field; a full-width accent button reading "Sign in"; and a final muted line offering account creation.

Fields: 1px hairline border, 7px radius, generous height, label above in small bold type.

This is the simpler sibling of the sign-up page: one field fewer and no hint text. Same card proportions and same vertical centring, so the two read as a pair.

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If the result is wrong, reply with one of these:
  Use the accent on exactly one element. Everything else is black, grey and white.
  Remove all gradients, shadows, rounded cards and illustrations. Flat, hairline rules only.
  Double the whitespace. Reduce to half the elements.

Dark theme: background #0a0a0a, raised #131313, primary text #f4f4f5, muted #9b9ba3, hairline #26262b, accent #4fc69a.
Mobile: render at 9:16, single column, hamburger in the top bar.
