You begin the game in the lower left corner of the map. Your first goal is to reach the first dungeon entrance in the upper left corner of the map, so you will have to climb up the left side of the fortress to reach it. There happens to be a dungeon entrance right where you start, but you don't have the correct idol key for it, so it won't do you any good to try to access it.
As soon as you begin the game, you will immediately face off with a Bouncer. If you are new to the game, this is your opportunity to practice fighting, and learn the best techniques for defeating your opponents. There are two primary strategies to adopt when fighting opponents; all-out offense, or mixed-in defense. With all-out offense, you get in very close, duck down, and strike as rapidly as you possibly can. Some of your strikes may be guarded against, but the hope is that you will end up damaging your opponent before they ever get a chance to strike you. The safer, yet slower strategy is the mixed-in defense. As long as you do not have any obstacles behind you, you can guard against an attack by pushing the direction pad backwards. If you guard an attack, you will almost always succeed with a counter attack. You can attempt to get two in before you switch back to guarding.
If you are a little more seasoned with the game, then ultimately you may choose to ignore this fight altogether, and simply jump over the Bouncer and proceed on your way. Don't forget to smash the wall to the right of the ladder to collect some of the items contained within.
As you climb up the first ladder, you may opt to take the longer detour to the right, but it is far faster to jump off to the left. Once you do, a short walk will lead you to a much more dangerous foe than the Bouncer; a Blaster. Blasters may be weak and easily defeated, but their guns pack an amazingly powerful punch that you should avoid at all costs! Move inside quickly, duck down, and defeat him as fast as possible. Avoid falling back down the hole before you defeat him or the enemy will regain all of its lost health.
Continue to venture up, and you will begin to encounter basic enemies like the caterpillar. Though they are small and easily defeated, they can be quite a nuisance, and difficult to clear. With the exception of the Sorcerer, you must squat down to defeat the smaller enemies. And the timing of your attack must be very precise. Be very careful and take the time it takes you to squat down into consideration. Most basic enemies have a limited range of territory that they can cover. It is useful to observe how they move before rushing in to attack so that you can stand safely outside their attack range. When you leave a screen and return, all basic enemies are restored.
Climb up through several more floors, dealing with small enemies as you encounter them, and remembering to collect all of the items that you come across. Along the way, you may come close to the location of the Armor body, but without the ability to break blue blocks, you will be unable to access it.
Note the passage below the area on the map marked with an A. While you may likely fall down the ladder to the ground below and have to deal with a caterpillar (remember to guard if you fall), it is possibly to bypass this fight by utilizing the double jump technique. In this case, you should attempt to jump over the ladder gap, and as you fall into the gap, strike the wall with an attack. As the attack is performed immediately press the jump button again, and you should be able to perform a second jump that will carry you up and over to the other side of the platform.
One last difficult area on the way to the dungeon is right when you arrive at the highest level. A bat is perched right on the ceiling above where you arrive. Jumping off the ladder safely requires precise timing. Continue to climb as the bat descends. When the bat is roughly halfway down the ladder, jump off to the left. If you have time, turn around and face right just in case you get hit. Proceed to the left, fight the Bouncer if you want to, then touch the orb which serves as the dungeon entrance.
The first enemy you encounter is a Caterpillar. You'll have to approach it carefully in order to avoid getting hurt. You must drop down the step to the floor in order to attack it, and you can't guard while crouching, so you should wait to approach it until it is moving to the left. Then drop down to the floor, crouch town, and attack it as it approaches. Caterpillar on the floor above requires similar timing.
Next up are two bats. The best way to deal with them is to turn around, face right, and walk backwards to the ladder to the left. This will automatically allow you to guard yourself against their attacks as they drop down.
When you make it to the very top floor, you must prepare to face off against the boss. While fighting against the boss can be a bit challenging, there is actually a way to make this fight incredibly easy. Destroy the left most statue statue at the bottom of the steps before the boss appears, and stand in the space of that statue. From that location, you can hit the boss without fear of getting hurt.
Once the boss is defeated, destroy the statue in the back to retrieve the DATT idol. Now you must turn around and make your way back to the dungeon entrance and back to the fortress. Be careful as you can actually get hurt more on your way out than you did going in. Remember to turn around and walk backwards when you pass beneath the bats.
One last note, remember that the Bouncer will be back in place when you return to the fortress. Move quickly from where you arrive to avoid getting dragged into a fight with it.