const ISLAND_THRESHOLD: f64 = _; // -0.89999997615814208f64Expand description
Threshold for simplex noise below which an island is spawned.
Vanilla uses -0.9F (float literal) in a double < float comparison, which
promotes the float to double. (double)(-0.9f) ≈ -0.8999999761581421,
NOT the exact double -0.9. We must match this f32→f64 promotion.