Approaching the limit of what TI-BASIC can do without busting out the modern calcs. Doing a simple operation on the whole 95x63 1bpp graph mode screen, say, turning all pixels on or off, takes over a minute. Add any sort of calculation to that...
I'm already using BASIC-callable machine code snippets to scroll the screen one pixel (which are nigh instantly finished,) and i'm so fucking tired of scrolling effects...

God, adding sound is gonna be a nightmare...

EDIT: for reference, dev machine is a TI-84+ Silver Edition. Not one of the ones with the eZ80 and backlit color screens, the greenish Z80 1bpp screened one. The one that's an 8MHz Zilog that TI decided to make multitask. The one where oscillating the screen at an integer division of full framerate fries it in seconds?