How to use @swim/interpolate - 1 common examples

const by = b.centerY.value! * bounds.height;
    const bColor = b.chargeColor.value!.darker(chargeDarken).alpha(chargeOpacity);

    const dt = now - a.t0;
    const pulseWidth = 2000;
    const halfPulse = pulseWidth / 2;
    let pulsePhase = (dt % pulseWidth) / halfPulse;
    if (pulsePhase > 1) {
      pulsePhase = 2 - pulsePhase;
    }

    context.lineWidth = 4;
    const gradient = context.createLinearGradient(ax, ay, bx, by);
    gradient.addColorStop(0, aColor.alpha(0).toString());
    if (pulsePhase !== 0 && pulsePhase !== 1) {
      const abColor = Interpolator.color(aColor, bColor).interpolate(pulsePhase);
      gradient.addColorStop(pulsePhase, abColor.toString());
    }
    gradient.addColorStop(1, bColor.alpha(0).toString());
    context.strokeStyle = gradient;

    context.beginPath();
    context.moveTo(ax, ay);
    context.lineTo(bx, by);
    context.stroke();
  }