A second playthrough, this time in Story mode, revealed some bugs: 1) The Bonus tally doesn't work, period. You get absolutely nothing added to your score after completing an act. 2) Finishing Story mode after Classic mode, even with 7 emeralds, re-locks the true final stage in Stage Select. 3) With the spike shield (and the magician powerup, which is when I noticed it, but I've seen it happen without), enemies around Sonic seem to spontaneously die. This was noticed as early as the first Zone, with the Sonic CD caterpillar enemies. 4) Hitboxes for some enemies need tweaked. If an enemy looks like it will pass harmlessly under Sonic, like in Red Hot Ride, then you should be able to stand on the platform above it, and not get hit.