Shellcore, known as "Blocken" (ブロッ拳 Burokken, a combination of the words block and fist) in Japan, is a martial art praticed in Radaxian. Alex Kidd is the only know praticer of Shellcore, which he learned from Saint Nurari.
The user is capable of giving strong hits, usually punches, capable of breaking stone blocks. A interesting feature is that this technique is that it appears to allow its user to grow the hand during a punch, although it is unknown if this is a feature from the attack or an artistic rendition of the technique in use, as the hands of characters are also bigger when playing Janken.
Although Shellcore is traditionally seen in punches, the technique can also be used with kicks. The Power Bracelet allows Alex to release "Shocking Waves of Destruction" (破断衝撃波 Hadan Shōgekiha, "Breaking Shockwave") from his punches, a powerful ancient technique in the Shellcore art.