Proper planning is key, both to ensure that you don't find yourself suddenly and unexpectedly needing 500 new images, and to find areas for optimization.<p>What's the value in having enemies have slight differences in appearance as they get close to death? Will players actually notice or care about this? In a 2D games, it probably makes a lot more economical sense to add some kind of procedural effect to show this, such as tinting them red, making them flash, or showing a bright red outline.
This is why video game companies hire more artists than programmers.<p>Counting frames is often not productive though, cut-out animations (which PvZ appears to be using) allow artists to render many frames from one base illustration and some extra work. They're not necessarily easy but they're often a large time savings over frame by frame.
This is incredibly true. I've been making a flash game recently, and it's my first, but I've just been overwhelmed with how many images are required.
At every step I'm realizing, "Oh damn, I need images for this. <i>Finds my graphics buddy</i>"
There have been some approaches to client-side image generation in computer games [1][2], but they're not very successful commercially.<p>1. <a href="http://ifarchive.jmac.org/" rel="nofollow">http://ifarchive.jmac.org/</a>
2. <a href="http://eblong.com/zarf/glulx/" rel="nofollow">http://eblong.com/zarf/glulx/</a>