First of all, Anilo, let me say how much I appreciate your creating the script and graphics for others to enjoy. And I do enjoy your work. I knew that the town center building should have flames dancing in front of it, but I was delighted to see also the water in the fountain. Such tiny detail. And every waterfront needs a working crane to load the ships. But what really made me laugh was the diplomat giving me such a look, like someone's leering avatar.
15 years ago, a 160 x 240 pixel animation at 15 frames per second was a staggering demand on computer resources and bandwidth [1.5 megabytes, oh my!]. On today's computers people watch full-screen high-definition video at 30 fps. But they don't do that over a 56 K modem connection or on a machine with 512 megs of RAM. The size of your little animations is not the problem. Nor is it a problem of Firefox, which always loads faster for me than Explorer.
My point is that rather than discontinuing a wonderful feature for Ikarium on a popular and innovative browser you could think about it this way:
>> You are more likely to hear from grumpy users than pleased ones. Sad but true.
>> Your answers to the whiners are very generous and helpful. I loved your information about editing the script. [My answer would be, if you don't like it, don't use it.]
>> Instead of losing the pleasure of creating something for so many, or denying those who enjoy your work for the reason that a few have problems, you may say to those with distracting slowness that instead of blaming your work, they could take responsibility for their pleasure by upgrading their computers to meet certain basic requirements, such as internet access via cable or DSL and having sufficient RAM.

RAM is the single most important upgrade to having a computer that is fun instead of being weak and slow. It is so cheap that you might say the minimum amount of RAM that you need is however much is the most RAM that your computer will take.
Anyway, I will stop now, for I am obviously a very crabby person, and your readers will want to get back to something more nice. But whatever you decide, do it for your own reasons. You have a worthwhile talent that will bring good however you express it. Do not let anyone discourage your enjoyment or sharing of it.
Regards,
musclemutt