Sunday, May 27, 2012

Story Mode

Save all humans

I'm now mid-through my second loop, which has a focus on mid term gameplay.

I first worked on implementing the 'save humans' mechanic. The basic idea is to collect humans a la Choplifter, then drop them to a safe place. Here's the 1982 original Apple II game for those of you too young to remember:

Now you can see that in Choplifter the helicopter has to land on the ground to collect the humans, a control mechanic that I don't have in my game (and I don't want to have). Remember my 'ship' only flies at two altitudes and is never able to actually land on the ground.

In Jesse Schell's excellent book 'The art of game design', I remember an interesting point about the advantages of designing a mechanic that can be reused in various contexts. It gives the player confidence and provides a sense of satisfaction because using a control he already knows he can explore new possibilities without new things to learn. It also relates to the amplification factor of the action as the player only have to learn to use a particular action once, but then the multiple possible reactions (or effects) depend on the context and amplify the control possibilities.

To comply with this idea of reusing existing mechanics, I decided to use the same 'slow-down to a stop' mechanic I developed for the fuel tank. This mechanic works at the lower altitude. As the little humans obviously should be on the ground, this altitude difference problem needs to be addressed.

The solution I developed is simply to have platforms on which the ship can stop, and having the little humans running toward the platform while the ship is waiting.

So I first made a generic human model with as few polygons as possible, yet enough for skinning animation to be implemented later:

There came the problem of scale. Should the humans be at a realistic scale given my building scale? Or should they be scaled up in order to better identify with them? I kinda did a compromise here, I made them small enough to integrate with the environment, yet large enough to read their features. I do think it works but I can change my mind later when designing final assets.

I then made the platforms. The one for collecting humans (blue), and the ones for unloading them (green).

Note the blue one having a solid collision mesh attached for the aliens to collide with it. The spheres are the triggers.

I think the player will easily relate to the fact that when a human disappears below the platform, he is being lifted to the cargo. I've added some stats to the HUD to help.

Of course the graphic design will have to be made in order to convey the function of the platform. But I could say that for all the gameplay assets of the game anyways.


As seen in the above screenshot, I've added portals to the gameplay elements. The idea is quite simple, you're given an objective at the beginning of a level, when this objective is fulfilled, the portal opens and you can move to the next level. It doesn't mean you have to do so however, you can continue collecting extra items or points until you decide to leave. That's basically the way I designed the success and failure condition within the scope of a level in order to create a first version of the Story Mode.

Again, I've made it all data driven, so here's a screen of a level with the new items added:

I've made it so you can associate as many humans to a platform by simply placing those humans in its vicinity. They will automatically run toward the closest platform. The percentage of accomplishment is automatically computed depending on the number of humans in a level.

Finally, the sequence of levels for the story mode and the objective to reach is simply defined in a lua table.

Enough talk, let's see how it plays:

A lot needs to be tuned but you get the idea. Now I need to work on designing some actual levels and objectives and see how that works. Next I'll have to work again on enemies behavior (which are a little rough right now) and add more variety to both enemies and items.

Oh and did I talk about exploration yet? I think this will play a large part in my game, but for that I'll need some actual graphic assets so all stuff doesn't look the same...

Hope you enjoyed this post, and as always feel free to comment.

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