jeudi, octobre 02, 2014

Kirby Kid's Advice: Inconsistent Spongebop

Inconsistent interactions with yellow things. The yellow swinging enemies are neat looking and they have neat physics to them. But interacting with them is very inconsistent and too complicated. It's hard to stay on top of them. It's hard to get the big jump off of them. And the momentum of their swing doesn't transfer to the player at all.
Let's first see what "inconsistent" means in this context. Kirby Kid validated the two definitions I formulated as below:

A mechanic is consistent with regards to 2 object if
  • applying it the same way on the two objects leads to the same result. E.g. slashing something with the sword breaks it into bits in Zelda series. That works on bushes, jars, skulls and even rocks in some games.
  • when it leads to different result, the objects shall be sufficiently different so that the player can easily tell what result it will get from passive analysis of the object. E.g. Jumping on an ennemy in SMB always attacks the ennemy unless the ennemy has spikes on his head. Moreover, the ennemy will always be defeated unless it is shelled.
A gameplay element (applying mechanic A on object B) is self-consistent if
  • it always produce the same result (e.g. bounce by 3 blocks height)
  • when producing different result, the player can relate the cause of this difference to visible difference of state. E.g. a spring that may be loose or compressed will throw you higher if compressed.

Pour corriger mon éponge-qui-se-balance, aussi connue sous le nom de "Spongebop" ou "Bop, l'éponge", je vais avoir un peu plus de mal. Kirby Kid lui a diagnostiqué un problème de manque de cohérence, ce que je peux traduire de la façon suivante: il n'existe pas de manière claire de savoir quel sera le résultat d'un rebond ou d'un balancer qui fait intervenir l'éponge. Kirby Kid mentionnait aussi le fait qu'il est difficile de déterminer si l'éponge va nous repousser vers le côté où si on va pouvoir atterrir dessus. La difficulté principale sera psychologique: dès les premiers coups de crayons, "Bop, l'éponge" est un personnage (et pas une plate-forme) au comportement erratique. Il sera utile, mais il faudra s'en méfier.

From the start I have designed spongebop to be somewhat chaotic, which makes it appear mostly only on the "hard path" of School Rush game. But chaotic must not mean "totally unpredictable". There are two moves that are expected with a sponge bop. The first is to use it to gain height, the other is to clear a larger distance with a jump. Both are based on the fact that, when you press A while un-grabbing a SpongeBop, its current velocity is added to the one of your jump.

Initially, I thought Kirby Kid was mostly criticizing the difficulty to do the first move -- gain height -- because when SpongeBop is  almost idle, the only moment when you can "jump off" is when it moves upwards. But getting that is more a matter of luck than skill: because oscillations of Spongebop across its equilibrium are small and that the "auto-bounce" that happens when you "land" on it can hardly be controlled, the best you can do is to try again and again until it works. You cannot even spam the JUMP button because you'll have to hold it down once successfully bouncing off if you don't want to cancel your jump.

Voyons un peu les interactions que permettent Spongebop:
  • SB peut pousser Bilou bas d'une plate-forme ou l'interrompre dans son saut si le contact est latéral. Incohérence: c'est un rectangle qui nous repousse alors que SB est un patatoïde protubérant.
  • Bilou peut rebondir sur SB s'il tombe dessus et rebondir plus haut s'il appuie sur (A) avec justesse. Incohérence: il est difficile de déterminer la hauteur qu'aura le saut effectué dans la plupart des cas.
  • Bilou peut s'accrocher à SB pour franchir plus facilement un trou. Incohérence: il n'est possible de s'accrocher que lorsqu'on tombe, et pas juste après un rebond malencontreux.
  • Bilou peut faire un long saut en avant en appuyant sur (A) au moment précis où l'on lache l'éponge. Incohérence: rien n'indique pour celui qui n'a pas encore suivi de cours de balistique (ou fait trop peu de balançoire) que la fin du mouvement est un mauvais moment pour cette manoeuvre-là.

 I've been more surprised to see Pierrick failing to clear a large jump by using SpongeBop's swinging speed. He was persistantly trying to jump *at the end* of the swing, but physically speaking, bop's momentum is nul at this time. So indeed, it doesn't transfer to your character.

The way Spongebop behaviour lacks consistency can be summarized as such: when you jump off a Spongebop, the velocity you have will depend on Spongebop's instant velocity. Due to its physics, Spongebop velocity is constantly changing in 2 dimension, meaning that it takes some careful study (or prior knowledge) to pick the moment where you'll get the desired behaviour.

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