Looks polished, and I got to level seven or so. Fun! The locked-in pieces were an interesting twist. Those could've used a clear "locked" icon or other marker. Liked the drag-and-drop mechanics. Small bug: When I dropped a two-letter block about midway onto a locked letter, it let me drop the block there. What else... Would have been nice to have visual or sound feedback to show when the letters are matched, esp. since the pairings aren't obvious to non-bio majors. A time limit would be a good nerve-wracking addition. If you wanted to, you could follow the "Balatro" trend by having some kind of scoring system where you manage some side-goal like including as many Ts as possible or you earn a permanent extra GG.