Gradient Illusion (Stepping Feet)
Watch the blue and yellow blocks. They are moving at the exact same constant speed. But they appear to speed up and slow down like feet walking.
Contrast Drives Motion
🏁 Low vs High Contrast▼
This effect is known as the **Stepping Feet Illusion**. Our brain processes high-contrast motion (black on white) faster than low-contrast motion (dark blue on black).
As the blocks pass over the stripes, their contrast flips back and forth. When contrast is low, the brain "loses" the edge slightly, making it look like it slows down. When contrast is high, it snaps forward.