Help writing SQL query

Hi, I have designed a table that contains the following information about some simple shapes

I need a bit of help writing some SQL (Oracle 8i/9i Enterprise). I would like to query the database and count, for example, the number of shapes with triangles in them. For all the data below this would return 2 (1 for the shape that is a triangle and 1 for the shape that is a rectangle made up of 2 triangles).

If the design is bad, I would appreciate constructive critism on what would be a better design - at this stage nothing is set in concrete
(initially I thought this would be an easy query to write using a
CONNECT BY PRIOR construct clause but this doesn't work for 'cyclic/loop data' like that below).
Many thanks
Tony

CREATE TABLE tblshapes(shapeID NUMBER,node NUMBER,nextnode_linkedlist NUMBER);

• RECTANGLE
• 1---------2
• | |
• | |
• | |
• 4---------3 -- INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (100,1,4);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (100,2,1);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (100,3,2);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (100,4,3);
  
• TRIANGLE
• 10
• |\
• | \
• | \
• | \
• 11---12 -- INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (200,10,12);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (200,11,10);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (200,12,11);
  
• TWO TRIANGLES ADDED TOGETHER TO MAKE A RECTANGLE
• 20----21
• |\ |
• | \ |
• | \ |
• | \|
• 23----22 -- INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (300,20,23);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (300,20,22);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (300,21,20);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (300,22,21);
  INSERT INTO tblshapes(shapeID,node,nextnode_linkedlist) VALUES
  (300,23,22);