Tip: Make sure that ALL exit-enabled pipes, doors, etc. have a screen exit defined, or they'll take you to Level 0, the "endless" bonus game. Unless Start+Select is enabled, the only way out of it is to reset the game.
Place the 7 blocks in any order you wish, but they are designed in such a way as to have one combination and only one. They must always be hit in order, 1, 2, 3, 4, 5, 6, 7. If you want to lay them out in a straight row in the order 4, 6, 3, 1, 7, 5, 2, they'll work the same way. These blocks may be set to act like whatever you wish.
Doors (door_block.asm) are activated if the correct code is put in.