Sounds like a problem with the game engine, 2d flys these days with a million sprites at once. Try a different engine, theres a really good 2d engine that goes really quick called torque 2d and it goes with a programming language that edits with torsion, to control behaviours, i learnt it in school. its made by garage games, goto www.garagegames.com that should fix all your problems. 1) something going wrong. 2) you need framerate for animation 3) ??? 4) torque is really really good for debugging 5) torque handles double buffering for you 6) youll have to learn c# to code with torque, but dont worry its pretty similar to basic anyway.

Just some potential answers below. 1. There are numerous reasons this could be happening. i) Are you CPU bound? If your CPU cannot preform logic fast enough, then your frame rates will drop. Solution? Batch polygons for rendering rather that loop through and render each individual polygon. Partition your scene and render only the pieces that are visible. Check for collision only with the pieces that are visible, and in some cases perform on AI on the monsters that are visible (or extend the visible range so AI kicks in before they show up on screen). ii) Are you GPU bound? If your GPU is struggling with fillrate, to many polygons, expensive shader effects? This could all lead to poor frame rate. Solution? Analyse your GPU code and try to optimize it where possible. Minimize your poly count and/or texture resolution (or use texture compression), avoid to many layers (fillrate issue), render front to back with opaque geometry and back to front with translucent objects. Make sure you're using vertex buffer objects for efficient rendering. 2. Use programming for animation whenever possible. Skeletal animations is widely used as is key frame animation. If you are using 2D sprite sheets (atlases), you may need to do some extra work. Some sprites may be able to use a skeletal animation system, but you would have to partition your characters into pieces so that you can apply bones to them. This has limited capability, but can work for some scenarios. 3. Why do they look terrible? 4. IMO, try to get accustomed to real-time debugging. Don't debug in fullscreen either, debug in window. Your next alternative is a good logging system. 5. You don't render twice. The backend will copy your back buffer (where you are rendering graphics) into the front buffer before being displayed. This smooths out the rendering of the front buffer, which otherwise would have rendered even if you were still working on it and would introduce that nasty frame tear/blinking effect. 6. Keep up to date on technology and programming designs and techniques. Find out how other people do things because you might learn something new that will help with your own developments and productivity.

It sounds like the trouble is in your double buffering. Maybe ask someone on a Purebasic forum if there is one how best to implement it. Otherwise do some study by googling. Most hardware doesn't have a problem keeping up with 2d anymore unless you are moving very large sprites. The only other problem might be that you aren't using hardware acceleration or you are under some kind of frame lock that is too low.