My laptop is comparable, except it is quad core and turbos to 3.4 ghz (870M gpu, but I run with intel hd 4600). I think the fact that your machine is a dual core i3 might be literally wiping the floor with our rendering performance. In that it can't render at all.
I've never skimped on CPU (for a very good reason) so I can't run tests on any devices that don't have a core basically free all the time. Here are a few reasons CPU performance might be important:
- Incredibly high draw call thoroughput is required for rendering many sprites with different textures.
- To reduce the number of draw calls, sprites are batched into groups with matching texture. Many sprite lists are generated by the CPU (walls and floors large offenders).
- (the above two ONLY HAPPEN WHEN SCROLLING PAST A 500px BOUND OR SMOOTH ZOOM, so they should not affect performance live)
- UI is not optimised at all. Many things are recalculated or rerendered during the draw step, instead of buffering elements that are unlikely to change any time soon. This will be very expensive to change.
Again, no way to fix this if I don't know what's causing it. I'm easily hitting 144 fps on a 680, since GPU will NEVER be the bottleneck in our rendering pipeline.