Gravitus on Cool Math Games
I found myself playing Gravitus around 2018, just killing time between classes. It sat on the Cool Math Games site as one of those space-themed arithmetic fighters. You control a planet, enemies appear with math problems on them, and you have to answer correctly to fire projectiles. That's essentially it. I ended up spending way too long on the harder difficulty settings because my mental math wasn't as sharp as I thought it was. The game runs entirely in-browser. No download required. You go to coolmathgames.com, type gravitus into search, and it loads. It uses HTML5 now, so it works on most modern browsers without Flash or any plugin nonsense. I tested it on an older laptop with Chrome and it ran fine at 60 frames per second on easier levels. The heavier levels with more on-screen objects pushed it to around 40 fps, which still felt playable.
Cool Math Games Gravitus
Here's how the actual gameplay works, not the marketing version. A math problem appears on an enemy ship. You select your answer from multiple choices or type it in, depending on the game mode. Get it right and your planet fires a shot. Miss or take too long and the enemy fires back. The game has different modes: practice mode for learning, versus mode against another player locally, and survival mode where waves get progressively harder. The difficulty curve is actually the most interesting part of this game. Early problems are simple addition and subtraction. Then it moves to multiplication tables. Then fractions. Then percentages. By the time you hit the late game, you're doing things like calculating compound interest or converting between metric and imperial units under pressure. I remember failing a survival run because I couldn't quickly figure out what 17% of 240 was while three enemies were closing in. That stuck with me longer than any textbook exercise would have. The sound design is decent but forgettable. There's a low hum when you're thinking about an answer and a satisfying crunch when you destroy an enemy. I played with headphones and it was fine. Without them, you miss the audio cues that tell you when you've answered incorrectly versus when time is running out.
One issue I ran into that nobody really talks about: the game doesn't save your progress between sessions unless you're logged into a Cool Math Games account, and even then the sync is spotty. I spent maybe six hours grinding through the survival mode on one device, then tried it on a different computer and my high score was gone. The workaround is simple enough — just make sure you're signed in and check your profile page after each session to confirm your data is actually syncing. It took me two failed attempts before I caught onto that pattern. There's also a localization quirk. If you switch your browser language to certain European languages, the decimal separator flips from a period to a comma. I didn't notice at first and got confused why my answer of 3.14 was being marked wrong when the correct format on screen showed 3,14. The game accepts both formats once you figure out what's happening, but it throws you off during a fast round. From an educational standpoint, the game covers arithmetic, percentages, fractions, basic geometry, and some unit conversion. It's not going to teach you algebra or anything beyond middle school math. If you're looking for that, you'd want something more structured. But for quick mental math drills, it does the job. I'd estimate it's roughly equivalent to doing thirty to fifty practice problems per hour, depending on how fast you can think.
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The multiplayer versus mode is local only. Two people on the same keyboard, taking turns or racing on the same problem set. It's fine for a quick match but don't expect online matchmaking. I tried hosting a session for a couple of friends once and setting it up took about thirty seconds, which was actually pretty clean. Performance wise, it's lightweight. I've seen it run on Chromebooks and tablets without issues. The only real bottleneck is input lag if you're on a very old browser or a machine with limited RAM. Upgrading to the latest Chrome or Firefox usually fixes any sluggishness. If you're looking for alternatives, there's Math Blaster and a few other browser-based math shooters, but Gravitus holds up well for what it is. It's not going to win any awards for innovation. The graphics are simple 2D sprites and the UI is functional at best. But it gets the math practice done without being boring about it, which is more than I can say for a lot of educational software I've tried over the years.
