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Quiz: Facial Anatomy & Layout Design

Test your understanding of how a face decomposes into independently parameterized parts, and how one draw_face() function assembles them all.

1. What does facial symmetry let a face designer avoid doing?

  1. Drawing eyebrows and a mouth in the same program
  2. Using the quadrant fill code for eyelids
  3. Working out the right eye's position as a separate problem from the left eye's
  4. Storing face parameters in a dictionary
Show Answer

The correct answer is C. Because most facial features mirror around a vertical centerline, you compute one side's offset from center and flip its sign for the other. One calculation, reflected, gives a balanced face for half the thinking. Symmetry is a default a neutral face follows, not a law — a wink or a single raised eyebrow deliberately breaks it.

Concept Tested: Facial Symmetry

See: Mirror Image: Facial Symmetry

2. What is a face state data structure?

  1. A dictionary bundling every current face parameter into one object representing a complete expression
  2. The frame buffer holding the currently displayed face image
  3. A list of every drawing method draw_face() will call, in order
  4. A record of which expressions the robot has shown most recently
Show Answer

The correct answer is A. The face state dictionary is a complete snapshot of one expression, frozen as data — keys like eye_size, eyebrow_angle, and mouth_curvature paired with plain numbers. Change one value and you have described a different emotion without touching any drawing code. The dictionary is the expression; the drawing functions just turn it into pixels.

Concept Tested: Face State Data Structure

See: Bundling the Numbers: Face State Data Structure

3. Using mirror_x(x, center_x), which returns center_x + (center_x - x), what is the right eye's x-position if the left eye sits at x = 44 and the centerline is at x = 64?

  1. 20
  2. 108
  3. 64
  4. 84
Show Answer

The correct answer is D. The left eye sits 20 pixels left of center (64 − 44 = 20), so the right eye sits 20 pixels right of center: 64 + 20 = 84. Option A is the distance from center rather than a coordinate, and option B would place the eye 44 pixels past center, doubling the offset by mistake.

Concept Tested: Facial Symmetry

See: Mirror Image: Facial Symmetry

4. How does a lowered eyelid get drawn without introducing any new drawing method?

  1. By calling fb.scroll() to shift the eye downward behind the face outline
  2. By redrawing the eye's top half in the background color using a quadrant mask
  3. By reducing the eye's yradius until only a thin sliver remains
  4. By blitting a pre-drawn eyelid sprite over the eye
Show Answer

The correct answer is B. Eyelid representation reuses Chapter 7's quadrant fill code directly: fb.ellipse(x, y, eye_size, eye_size, background_color, True, TOP_HALF) covers the upper two quadrants of an already-drawn eye. One extra call after draw_eyes() produces a half-closed, sleepy look — no new shape, no new method.

Concept Tested: Eyelid Representation

See: Half-Closed and Sleepy: Eyelid Representation

5. A face built for the 128x64 OLED looks tiny and clustered in one corner of the 240x240 round display. What is the right fix?

  1. Redraw every feature at twice its pixel size by hand
  2. Move the origin to the center of the round display
  3. Increase the frame buffer's bit depth to match the color display
  4. Compute each parameter as a fraction of the display's width and height instead of a fixed pixel count
Show Answer

The correct answer is D. Feature scaling for screen size means writing eye_size = height // 8 rather than eye_size = 8. Calling default_face_state(128, 64) then produces OLED-sized values and default_face_state(240, 240) produces proportionally larger ones from the identical function body — draw_face() itself never changes, only the width and height passed in.

Concept Tested: Feature Scaling For Screen Size

See: Same Code, Every Screen

6. Why is an eyebrow_angle parameter better than hardcoding the exact point array for an angry eyebrow?

  1. A hardcoded array uses more memory than a computed one
  2. fb.poly() rejects point arrays that were typed in by hand
  3. A hardcoded array works once, but any variation or mirrored version must be recomputed from scratch by hand
  4. A hardcoded array cannot be filled, only outlined
Show Answer

The correct answer is C. Typing in "the angry eyebrow" you want right now works exactly once. The moment you need a slightly less furrowed version, or the mirrored shape for a wink, you would redo the coordinates by hand. One parameter you can change with a single number is worth the extra few lines of setup every time.

Concept Tested: Eyebrow Angle Parameter

See: Shaping a Mood: Eyebrow Shape and Eyebrow Angle Parameter

7. In what order does draw_face() draw a face's features?

  1. Smallest details first, then progressively larger shapes, then the background
  2. Background, face outline, eyebrows, eyes, then pupils and mouth
  3. Whatever order the keys appear in the face state dictionary
  4. Eyes first, since they carry the most emotional weight
Show Answer

The correct answer is B. Largest and farthest-back shapes come first; smallest and most detailed shapes come last. This is not arbitrary — it is the same draw call order optimization Chapter 6 taught, now applied to a full face, so no feature is buried under something drawn after it and overdraw stays low.

Concept Tested: Draw Face Function

See: Putting Every Piece Together: The Draw Face Function

8. What does a mouth_curvature of 0 produce, given that curvature becomes the mouth ellipse's yradius?

  1. A nearly flat line, reading as a calm, neutral mouth
  2. A deep frown, since 0 counts as negative curvature
  3. An error, because an ellipse radius cannot be zero
  4. A perfectly round mouth, since both radii would then match
Show Answer

The correct answer is A. With yradius at 0, the bottom-half curve flattens into something very close to the straight fb.hline() mouth from Chapter 6 — without needing a separate function or method. That single special case is why one draw_mouth() covers smiles, frowns, and neutral expressions alike.

Concept Tested: Mouth Curvature Parameter

See: Curving a Mouth

9. What practical benefit does feature independence give a face-drawing program?

  1. It guarantees every feature stays within the display's bounding box
  2. It reduces the total memory the frame buffer needs
  3. One feature can be redesigned, tested, or replaced without touching any other feature's code
  4. It removes the need to call fb.show() after drawing
Show Answer

The correct answer is C. Because draw_eyebrow() knows nothing about how draw_mouth() computes its curve, each can be debugged on its own and swapped out freely. It also means new features — blush marks in Chapter 11, blinking in Chapter 12 — arrive as one new function rather than edits scattered across every existing one.

Concept Tested: Feature Independence

See: A Design Principle, Not Just a Mechanic: Feature Independence

10. Why are a nose and cheeks treated as optional on most faces in this book?

  1. They cannot be drawn with fb.ellipse() or fb.poly()
  2. They consume too much frame buffer memory to redraw each frame
  3. They break facial symmetry and so complicate the mirroring math
  4. Research shows eyes, eyebrows, and a mouth carry almost all of a face's readable emotion
Show Answer

The correct answer is D. A nose is usually a short vline() tick and cheeks a couple of pixels — enough to make a face look more face-shaped, but contributing little to which emotion a viewer reads. Chapters 10 and 11 explain the research behind that finding, which is why the emotional heavy lifting stays with the eyes, eyebrows, and mouth.

Concept Tested: Nose Representation

See: Small But Not Unimportant