[NotStein]

Yea, viewing from the outside (a higher dimension, 3D vs. the 2D universe of the balloon surface), the lines aren't straight and it's not an equilateral triangle. But for the balloon universe, the lines are straight, 3*60, and it's an equilateral triangle to them, 'cause their measuring sticks also reside 'in' the balloon surface, and are just as curved as the triangle. Think of the meridians (great circles) going from pole-to-pole around the earth. They would appear to be straight lines running N-S to us on the surface, but someone floating above could easily see they're not, because the curvature on the surface is very apparent to them, while its not to us. This is only an visual approximation, 'cause in the real universe, it's the fabric of space-time itself that's curved (which curves our measuring sticks), and is much harder to visualize.