Simple Bullet Shadowing Surfer

This is not correct, although I've made the same mistake the first time thinking about this.

The catch point is that, even if your bullet passed safely, you know the intersection must contain no bullet, so the shadow of the bullet still exists

Sorry, I fixed the code.

My point was: Wouldn't it be smarter to deduct (100 - x) percent of the danger if the chance of the bullet colliding is x percent.

This is incorrect, because bullet shadow has nothing to do with whether bullets collide or not — it’s all about information. You know perfectly you won’t get hit in the shadow, so danger is 0. You still get hit by the part outside of shadow in the incoming wave though.

Let's say we have wave1(distanceTraveled 300) and wave2(distanceTraveled 100).

I shoot a bullet and it is calculated that it will intersect with wave2 at the x point so I set the danger to 0.

The bullet collides with the bullet that is on wave1 and the spot on wave2 isn't safe anymore.

Okay, I think I get it. Would the formula be

 PositionDanger = bulletPassedWave == true ? 0 : normalDanger

And if you are surfing multiple waves, you can estimate the chance that the wave2 will have a shadow by calculating in the percent chance the bullet will collide and add that to your calculations. Of course, once wave1 breaks, you can know for sure whether the position is 100% safe or not.