Every halving period (210,000 blocks, ~4y) there is a bull market in which bitcoin price pumps. Now listen carefully: these price pumps are NOT bubbles, but fundamental jumps, structural events, phase changes. You can see it in the realized price, which flattens, until the next jump. Halvings are critically important bitcoin events. S2F model tries to model these jumps as elegant as possible, with only 1 variable and a linear function.