No ship can sail straight into the wind. Come within about 40° of it and the sails stop pulling, flap loose, and the boat stalls — sailors call it being in irons. To make ground upwind you must tack: zig-zag across the wind on a slant.
Sailing down the coast of West Africa was easy — the north-east trade winds blew Portugal's caravels south. Coming home was the trap: those same winds were dead against a ship that hugged the coast, and it could crawl for weeks.
The answer was the volta do mar — the “turn of the sea.” Instead of fighting up the coast, ships sailed a huge arc west into the open Atlantic, then north to catch the westerlies, which carried them home. You sail away from home to reach it faster.
Reading this ring of winds — the North Atlantic gyre — was the real technology of the age. The same trick soon opened the sea road to the Americas.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.