You said the game lacks a level select, but there is one. Sort of...
When you complete a level it becomes available in the Score Attack mode. You can practice playing the level and after a few runs the levels can be relatively easy.
I've read and can vouch that the game can be played from beginning to end in 45 to 60 minutes, depending on how you play the game and what paths you take.
Paths? When you fight the bosses, or depending on which path you take in a level, the game guides you to different paths, so levels 2, 3 and 6 can be different from game to game.
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