About the Aurora effect
Aurora adds three sine waves together: one running horizontally, one vertically in the opposite direction, and one along the diagonal. Their sum is mapped onto the five-level block ramp ( ░▒▓█ ), producing broad, soft bands of light that ripple and fold across the whole screen like the northern lights. Because the three components move at different speeds, the bands keep reorganising: curtains form, thin out and merge again. The block characters give the effect a heavier, more luminous feel than symbol-based ramps, and at small font sizes the shading blends into near-continuous gradients. Green is the obvious aurora color, but purple and cyan mimic the rarer high-altitude displays. Keep the speed low, around 0.5×, for a slow, atmospheric drift that suits ambient streams, meditation timers and dark-mode hero sections.