My old C2 (browser) game runs very slow with the C3 runtime. What could be causing this? (SOLVED)

It seems to be running fine here. Construct provides tools for you to check performance and investigate why things are slow if you run the debugger and look at the profile tabs. That's the first place to go.

To be clear, the version I linked was using the C2 runtime.

When I load that program and choose the C2 runtime, it takes 12.89 seconds for my text message to scroll up the screen and the next scene to fade in. If I then choose the C3 runtime, the same sequence takes 56.25 seconds. So I'm clearly doing *something* wrong.

Okay, I just checked the debugger with both the C2 runtime and the C3 runtime. I'm not an expert but everything *seems* okay, except I did notice a big difference in CPU usage. During the text scroll:

C2 RUNTIME: 60 fps and 92% CPU

C3 RUNTIME: 26 fps and 1.8% CPU

I wouldn't mind taking a look at it if you want don't mind sending the capx but if not I can only suggest maybe change the max texture size in project settings?

Btw, I played it and I thought I was going to try one level but ended up finishing it chickka rakka chikka boom

Because of the music and large image files my .capx is HUGE. But thanks for the offer. If I can't figure out what's going on I may take you up on it. :-)

You finished it??? I'm kind of surprised (and impressed) because I tend to make some of the eggs way too difficult (as in practically impossible) to find. Gonna be better about that with this year's version. Heh.

C3 RUNTIME: 26 fps and 1.8% CPU

If you look in the profiler tabs you can get much more detailed information about both the CPU and GPU usage.

However given the low CPU usage and low FPS, I would guess you have an older device that's in the few % of systems that get kicked down to software rendering. The C3 runtime only uses WebGL so presumably with the C2 runtime you're getting canvas2d rendering only (which is possibly hardware accelerated, since it has lesser requirements). Try installing any software updates or updating the graphics driver. Most modern devices should be fine. Assuming you're using Chrome you can get more detailed information by visiting chrome://gpu in the address bar.

Also the framerate shouldn't affect the speed anything happens if you correctly use delta-time.