The game has four different last levels (and endings) depending on the conditions fulfilled during the game.
Each level is divided into three colors, called "Borders". Green is easy, Yellow is normal, Red is maniac. There is also score requirement on each stage, called "Norm". To reach the appropriate last level, you need to stay on a certain Border and get enough points to get the Norm cleared.
Stage 6A: Spend less than 50% on any border, and/or get less than 4 Norm clears.
Stage 6B: Spend at least 50% of the time on the green Border, and get more than 4 Norm clears.
Stage 6C: Spend at least 50% of the time on the yellow Border, and get more than 4 Norm clears.
Stage 6D: Spend at least 50% of the time on the red Border, and get more than 4 Norm clears.