From Landing Site A, take the cannon towards the rickety old Junction and then on to Zipline Station Charlie. Continue on the straight path until Powerworks. Yank the fallen gear up into the air, then charge blast it into place. Now you're the proud new owner of a Spider Ball, first introduced in Metroid II! With this fancy doohickey, you can revisit tons of old locations and rack up the missile count. Rather than get sidetracked, however, let's move on to the bottom of Powerworks. Follow the Spider Ball track to the end, then look to your left and see another track that doubles back the way you came. Follow it to a nearby set of missiles (boosting while on the track makes you jump straight out, by the way). Then, once back outside, Screw Attack to the nearby platform that houses a rather ornamental Spider Ball track. Stick to it and you'll find an Energy Tank halfway through.

From this point you could leave and head back to the Pirate Homeworld, but there's an Energy Cell not too far away. You have to collect these anyway, so let's go ahead and nab it - you'll be glad you did once you finally visit the Valhalla. First, head back to Construction Bay, where you can now use the Grapple Voltage to power up a Morph elevator. Once up top, look south. Screw Attack out to the missiles and scan the new lore entry. Then move into Ballista Storage, take care of the miniboss and claim your new Energy Cell. From here you can again leave, or head back to the Chozo Observatory for item locations on the remaining planets. It's up to you. Us, we're itching to get at the Nova Beam and acid armor back on the Pirate Homeworld. The next mission? Disable the Defense System.

First head to the Research Facility, back to the question mark on your radar. Along the way you'll pass through Scrapvault again. Hit up that Morph maze from earlier to grab the ship missile extension like so:

Once you're in the question mark room, use the nearby Spider track to attack this brief puzzle:

Head back to Metroid Processing and go through the white door. An easy missile expansion awaits behind the bomb-weary panel on the floor. Continue forward to Metroid Creche, where after a bit of bombing, you'll face a rather annoying miniboss. Just blast the arms until they're gone, yank one off and continue. After it's dead, use the Spider track on the ceiling to get another Energy Tank, unlock the Screw Attack platforms and continue on to a save point. Take the train back to the Command Center, then head back to Command Courtyard and deactivate the shield. Proceed through the Morph hole in the ext room and you'll appear back in Defense Access. Drain the shield then proceed up the Spider rail. Transit Station 4-A will whisk you to the next section.

Once at Phazon Quarry, use the drill to break away the right and left pieces of rock. Right gives you missiles, left lets you move on. After several straightforward rooms, you'll enter Main Cavern, which contains a quick miniboss battle that has you hurling enemies into a laser until it overloads. Be sure their armor is missing before the drill begins its "sucking" phase, then blast them loose. Now you have a Nova Beam and can finally shut down the damn shield.