Unfortunately the game's pretty intensive, especially the webgl version, given the amount of lights we put in. Were you able to run fine on the downloadable version? It should perform much better than the web version.
What kind of computer are you running this on? Can you describe the glitches? Admittedly the game's glitchy (some screen tears and parts of the screen become a solid red/orange for a second or two) on my computer as well, but my computer's been needing service and people with better computers run the game without a problem. If your computer's spec is too low then there's not much I can do.