I liked the concept and overall presentation, though I feel there could be a few more graphics effects sprinkled here and there. Also, maybe go for higher-res graphics for llama and sparkles, considering the squares are smoothly rotated anyway <- note: I prefer hi-res graphics to pixel art in general, given similar quality.
Going through one tunnel after another was pretty fun for a while, but the game never seemed to end while not offering any extra variation compared to, say, wave 5 (just going faster and with sharper "turns"). I eventually stopped at wave 17. If you were to expand upon that idea, I recommend adding extra gameplay elements to keep things fresh.