Paint mixes by subtraction. Each pigment is a filter: it soaks up some wavelengths and bounces the rest back. Blend two pigments and you keep only the light that both agree to reflect — so a mix is always darker than what you started with.
A screen does the opposite. It adds coloured light, so mixing there gets brighter. That is why the colours you pick on a monitor almost never behave the same way in real paint — the dashed marker shows the screen's answer, the solid one shows the pigment's.
Opposite colours on the wheel are complements. Together they absorb nearly everything, so they cancel to a muddy grey. Neighbours are analogous — they overlap, stay saturated, and read as a harmony.
To make a colour look brighter, you rarely just add white — that lifts the value but drains the saturation, giving a chalky tint. The value bar and the wheel radius are two different dials.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.