gems are lit up for certain modes such as fireball frenzy that indicate they are shots to be made. The HOADC inserts are for a "bonus" game within the game in which the player attempts to collect certain horse color patterns and then collects by hitting the collect shot behind the upper right flipper. Not enough going on in the game so they threw in a HOADC to scramble the last braincell not dealing with the stacks and RGB lights blowing up. Not a game for the weak minded.