GBGames

Oracle’s Eye is really shaping up as a game. I’m awfully close to the project, of course, so there could be lots of things wrong with it, but it’s definitely much more playable than when I called it “technically completed” a few weeks ago.

The links from December 9th still reflect the game’s current state, which means I haven’t done too much to update it. I made the Player’s sprite smaller and haven’t been able to walk through walls so far. Some of the small tweaks I’ve made with the code have made drastic changes in the resulting gameplay. For example, I combined two sections of code knowing that it wasn’t exactly what I wanted. I just wanted to get closer to whatever it was I was doing. The result: now instead of just pushing the Ball, you can push against the Walls, and depending on the direction you are facing, the Ball moves. Psychic powers?! Maybe I could make some Walls into switches that create a gravitational pull on the Ball? It might be an interesting gameplay development.

Of course, I haven’t exactly created or updated a detailed design, so how can I know when something is progress or the introduction of a bug? This project is starting to become a bit more concrete, so I think it is appropriate to list specific implementation goals. Since I’ve gotten this far, I really think it would be appropriate to turn it into a commercial quality game. Besides having a game to sell, it would also allow me to have the experience of finishing a game that doesn’t look and feel like a newbie’s first project.

It’s clear that Oracle’s Eye is becoming more like a puzzle game than anything else. The basic premise: maneuver the Ball through the Room to get to the Exit. Maybe that’s all a player needs to know, but what about me? I’m still making it!

• The Player should not be able to occupy the same space as a Ball. If the Ball hits a Wall, the Player should find that he/she needs to push at the Ball from a direction that isn’t towards the Wall in question. The point is to force the Player to use the level layout to find the best way to move the Ball. Allowing the Player to move the Ball through him/her would break the game since the Player would not need to worry about where certain Walls are.
• Graphics: the Ball should rotate when it is moving and in a way that implies rolling. As it stands,the Ball rotates in only one direction, and while it might not be too noticeable, it is incorrect. Similarly, the Player should have images from multiple angles and various key frames. The static Player image is fine for placeholder art, but it will need to be replaced by someone that looks alive and breathing. The Ball and the Wall and Floor tiles should also be updated with higher quality art. The graphic style should be cartoonish but not exaggerated.
• Sound: the game is silent currently. I should work on getting at least one piece of music for the background. The music should be upbeat and fun. There should also be sound effects for the Player when he/she kicks the Ball or hits a Wall. There should also be sound effects for the Ball hitting a Wall or getting to the Exit.
• Levels: each level will consist of a Room with Floor and Wall tiles, an Exit, and a starting location for the Ball and Player. Rooms should be able to have different dimensions. One Room might be 10×10, another might be 5×15, and another might have varying widths. The purpose is to allow vastly different level designs as well as varying visuals. The maximum limit is related to the screen dimensions and the Tile lengths. The Player should be able to choose levels from a menu, and finishing one level should allow him/her to continue to the next one. I imagine that the game would require the ability to restart a level if the Ball gets stuck in a corner or gets in some other situation that prevents Player progress.

I was about to add that I wanted extra items, like angled banks for the Ball to bounce in new directions, but I already decided to cut out such features. It’s a nice-to-have, and maybe I’ll find that it will be easy to add, but the above listing is what I want to concentrate on. I think that focusing on these things will greatly improve the game, and I can always write down the gameplay elements I come across that don’t fit this design but might be useful elsewhere. I will keep an offline version of what I have here. It should be easy to update as I gain more insight into the project and its needs. I already know that this isn’t nearly detailed enough, but it should be good enough to show you (and me!) what I’ll be working on.

Working off of the list of improvements for Oracle’s Eye, I managed to improve the hit detection somewhat.

I was originally thinking about changing the movement code completely. Instead of freely moving about, the Player and Ball would move in a tile-based manner. I spent a bit of time thinking and writing about how I would go about implementing a tile-based game, and I still believe that it might make some things easier. I could also start adding different objects easily.

But when I sat down to code, I decided to continue to do what seems to work for me: mold the existing project until it works.

A major problem with the movement is that the Ball can get stuck in Walls. It can bounce back out normally, but if the Player is too close, it will get stuck in the Wall. Unfortunately, one of the ways I tried to avoid problems with movement causes a very annoying bug. If the Ball moves into the Wall, it is supposed to move back out at twice the distance. It looks like it bounces back out. But if the Player is touching the Ball, it stops moving. Well, if it stops moving, it won’t bounce back because the reverse of stationary doesn’t exist! The next update through, if the Player moves, the Ball wants to move with the Player; however, because it is stuck in the Wall, it “bounces back”. The result is that the Ball looks like it is going the exact opposite way that the Player would expect, which makes the game feel buggy. And not the good, on-purpose buggy, either.

I’m not a fan of guessing with my code. If X = X + 1 doesn’t seem to work, I don’t just automatically turn it into X = X – 1. I prefer to analyze my code and try to determine what exactly is going wrong. In this case, I found that each update, the Player moves, then the Ball moves. Then the Kyra engine’s tree is walked, which allows me to accurately handle collision detection. The next step is to check if the Player collided with a Wall. No problem there. I just reverse the direction of the Player, move him, then change his direction to STOPPED. Then I check if the Player collided with the Ball. If it does, then the Ball will take on the direction of the Player. It makes sense in most cases. If the Player touches a stationary Ball, the Ball should act as if it had been kicked in the same direction that the Player was moving.

When the Ball is near a Wall, however, the Player can kick a Ball, and the Ball can bounce off the Wall. Now the Player and the Ball overlap. Again, it is not a big problem. If the Player moves, the Ball follows the Player. The problem occurs when the two overlap AND the Ball is overlapping the Wall. The Player moves, makes the Ball move, but then the Ball wants to reverse itself.

I found that most of the Ball/Wall overlap can be avoided by changing the order of the collision checking code. The Ball will check for collisions first, then the Player will do the same. The Ball might still get stuck in the Wall, but I’ve found that it is a quite a bit more rare and not as dire a situation. It is a lot harder to reproduce the issue, but of course, right when I was about to say that the problem was completely solved, it occurred.

In any case, it was a quick fix and didn’t require any new code. I’ll probably continue to work on this same issue, but for now it has been vastly improved. I think I will also want to change the size of the Ball. The diameter of the Ball is the width of a Tile, which makes it very difficult to maneuver. If there is a single Tile opening between two Walls, a player might find it incredibly frustrating to try to get the Ball in between. It is part of the reason why I was thinking about using Tile based movement. I should eliminate this problem entirely. Of course, Duke Nukem Forever has had its engine gutted and replaced a number of times, and I would actually like to complete this game soon. B-)

Download files: EDIT: I decided to take down this set of downloads. For both tar.gz and .zip files, it comes to about 16.5MB, and I’m running out of space on my server apparently. This update doesn’t exactly merit its own release, so I will remove it and allow space for better uploads.