Earth's rotation axis is tilted 23.4° and points the same way in space all year. For half the orbit the north pole leans toward the Sun (June solstice): sunlight hits the north more steeply (higher noon Sun) and days are longer, so the north heats up — summer. Six months later it leans away — winter. At the March and September equinoxes both hemispheres get 12-hour days.

Try this: ① Untick "keep the tilt" — the subsolar point locks onto the equator, every latitude gets 12-hour days, and the seasons vanish. ② Slide your latitude to the Arctic (66°+ in summer) to see the midnight Sun (24 h day). ③ Watch the terminator (day–night line) in the 3D view as you drag the date. ④ Compare June vs December noon Sun altitude at your latitude — that angle, not distance, is the whole story (Earth is actually closest to the Sun in early January!).

Distances and Earth's size are exaggerated for clarity; the tilt angle, day lengths and Sun angles are computed with the real formulas.