Back in March, Ars wrote about PhD student Michael Cook and his artificial intelligence machine called Angelina. Angelina was special because she was creating games from scratch with little help from her human counterparts. By dividing the concept of a computer game up into three defined “species,” or sub-tasks—maps, layouts, and rulesets—Cook and his compatriots at Imperial College in London helped their system auto-generate some simple platformer games.
On Friday, however, Cook released a game called A Puzzling Present which shows off the much of the hard work Cook's put into Angelina (a tail-recursive acronym for "A Novel Game-Evolving Labrat I've Named ANGELINA"). Instead of a simple platformer with maps and obstacles, the latest games by Angelina now include new mechanics for the player (in this particular seasonal game, the character is Santa Claus) at each level. For example, in World 1 of A Puzzling Present, hitting x (or a touch-screen b key in the mobile version) gives Santa an anti-gravity power that sends him to the top of the screen and hitting x again sends him back down. In the second World, hitting x gives Santa an elasticity function, which causes him to bounce ever faster against the surroundings above and below him. These mechanics, Cook says, were created artificially by ANGELINA for this particular game as part of a new system he developed called Mechanic Miner.
Mining for fun
On his blog, Cook laid out how Mechanic Miner works: start with a level you can't normally solve (because of a randomly-generated and damningly high wall, for example), invent a new mechanic that could help solve this level (like the ability to jump very high, or bounce off walls), and then test the level for playability.
Cook says he hadn't planned on building Mechanic Miner back in March. But creating the system became possible when he discovered flixel-android—a Java port of a game library called Flixel—which allows Angelina to bridge the gap between Java (which Angelina understands) and ActionScript (which platform games are written in). “It was really a way of letting ANGELINA make changes to a game directly, and then be able to see what effect those changes had, by simulating the game,” Cook told Ars in an e-mail.
The result is something a little closer to a game a human might be interested in investing an entire train commute in playing. Whereas before Angelina generated rulesets that defined the way the players obstacles appear in the games, Cook says his Miner is trying to replace that parameter with “something more flexible and much more interesting.”
Polling the humans
If you play A Puzzling Present on a PC or on your Android phone (available for free from the Google Play store!) you'll also notice that after each level a screen comes up asking how enjoyable and how difficult the level was. Cook said in March Angelina had trouble assessing level difficultly. While he experimented with having her “interact” with Twitter, A Puzzling Present is partly a way of collecting feedback that Cook can use to hone Angelina's knowledge of difficulty in a level. “Mechanic Miner lets ANGELINA simulate games in much finer detail,” Cook said. “It can now model things like the player's reaction time, for instance.”
This audience polling may be key to the evolution of Angelina. Cook explained:
“There's no human involved between finding a mechanic and designing levels for it—once it's found a potential game mechanic, it can start making levels right away. So you have to think carefully about what kind of level designer the system should have. Should it make long levels? Levels that need quick reaction time? Lots of thinking? Jumps? No jumps?
“In A Puzzling Present, all the mechanics use the same level designer. But I'm hoping the data from the game will show that mechanics can be very different and need very different level designers to take advantage of them. So it's still early days for ANGELINA's difficulty assessment...In the final game, the worlds and levels are randomized, so we can interpret the data better and with less bias. So you won't know what's coming next—but it'll help ANGELINA know better for the future!”
Humans and game bots, working together
After playing the finished product of A Puzzling Present on my Android phone for 20 or 30 minutes (the levels go by very quickly), I was quite surprised at how much more the addition of a single game mechanic in each world held my interest. The earlier platformers created by Angelina were cute and novel, but a little too uniform. So does this mean the end is nigh for game developers, especially those who work on quick and easy mobile phone games? Cook, at least, is of the opinion that nothing could be further from the truth.
“Actually I think Mechanic Miner is the first bit of research from the ANGELINA project that could really benefit the mainstream industry, rather than threaten it! If this technology was built into tools given to designers... it could suggest new game concepts or alterations to levels...[Wi]th Mechanic Miner, ANGELINA is more independent of humans than it has been previously. It's suggested mechanics to me that I wouldn't have thought of. It's found exploits in my code and used them to design levels I couldn't have dreamed of. That's fascinating stuff, and if we can create software that can actually suggest things that are novel to humans, then that's really exciting.”
Cook also reminded us that Angelina still doesn't create themes, art, or the music that polish off the games she creates. Humans are responsible for the graphics and the adorable crunch of the snow under Santa's feet as you walk around in A Puzzling Present.
And for longer games, with narrative arc, Cook says humanity is an irreplaceable factor in creating a game that connects with people. “We'll always enjoy ANGELINA's work, but when I read things like Edmund McMillen's postmortem of The Binding of Isaac in which he talks about his relationship with religion and how it affected his work—that's something uniquely important. I feel like the game is a bit richer because it had that person's input into it. Even if I can't really feel the difference, it's all wrapped up in the culture surrounding that particular game.”
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