Doubling ship toughness, and duels that wouldn't end

What we changed

On October 9, fights ended too quickly, since two missiles took an enemy down. We doubled every ship’s toughness, the player’s included. Toughness is the number each blow is divided by before it does damage, so doubling it should make a ship last about twice as long.

What we measured

The game has a tool that flies two computer pilots against each other in a small city of blocks, hundreds of duels at a time, much faster than real time. We use it to tune the enemy pilots: two versions fly the same duels, swapping sides, and the tool reports which one wins more. A duel that runs out of time is a draw.

After the change, almost every duel was a draw, and longer duels did not fix it.

At the end of five minutes, 95 of the 132 ships still flying had more than 60% of their hull; the median was 76%.

Why

Every ship has a shield in front of its hull. The shield takes damage first. Once nothing has hit it for 4 seconds it starts to refill, and it goes from empty to full in 3 seconds.

The toughness division happened before the shield took the blow. Doubling toughness halved every blow, and the shield then held twice as many hits. The computer pilots fight in passes: an attack run, then a break to reposition, which often takes long enough for the shield to refill. An attack run that used to get through the shield and into the hull now ended on the shield, and the hull came out of it untouched, so most passes did no hull damage at all.

What we did

We decided that toughness shouldn’t apply to shields. The shield now takes each blow whole, and toughness divides only what gets past it to the hull. The same 80 match-ups, five minutes each:

The player’s cannon now needs 104 rounds to bring down a medium enemy. By the same arithmetic it needed 64 before the change, and 128 with the shield divided too.

We also decided that a duel never ends in a draw. One still going at five minutes is now decided on points: the ship with more of its hull left wins, then the one that lost less over the duel, and if neither ship was touched, a coin toss drawn from the duel’s seed. In the 80 duels above, 13 went to points and none to the toss.