Exercise 1: A Missing Lighting Clamp With Two Lights on the Chest — Possible Solution
====================================================================

WHAT WOULD HAPPEN WITHOUT THE CLAMP
------------------------------
This chapter's Step 3 reused Chapter 4's own verified numbers: the
chest lid's normal dotted with a light in front gives a positive
brightness of approximately 0.6069, while the same normal dotted with
a light positioned behind the lid gives a NEGATIVE value of
approximately -0.6069. If the lighting code sums each light's
contribution and only clamps the final total once at the end (a
common, efficient design, as this course's Numerical Methods &
Floating-Point Computation material discussed), the light in front
would contribute +0.6069 to the running total, but the light behind
the chest would contribute -0.6069 - actively SUBTRACTING from the
total brightness rather than contributing nothing.

THE VISIBLE RESULT
------------------------------
Summing both contributions before any clamp: 0.6069 + (-0.6069) = 0.
The chest lid would render as if it were receiving NO light at all -
completely black or unlit - even though one of the two lights is
genuinely, correctly illuminating it from the front. A player looking
at the scene would see the chest's lid go dark specifically because a
second light was added somewhere behind it, which is physically
backwards: adding a light source should never make a surface appear
darker than it would with fewer lights.

WHY THIS IS A REAL, PLAUSIBLE BUG RATHER THAN A CONTRIVED ONE
------------------------------
This is exactly the multi-light summing scenario described as the
place this bug becomes clearly visible, since with only one light in
a test scene, an incidental downstream clamp (for example, when
converting a brightness value to an 8-bit color channel) can mask a
missing max(0, ...) check without anyone noticing - it's specifically
when multiple lights are combined before that final clamp that a
light behind an object can meaningfully cancel out a light in front
of it.

WHY THIS WORKS AS AN ANSWER
------------------------------
The explanation uses this chapter's own specific reused numbers
(0.6069 and -0.6069) to compute the exact resulting sum rather than
describing the bug only qualitatively, and identifies the precise,
physically nonsensical visible symptom (the chest going dark when a
second light is added) that would result.