< Radical
Radical 31 is the "surrounding box" radical, not to be confused with the "little mouth" radical.
+0 Strokes
囗
+2 Strokes
囚 , 四
+3 Strokes
回 , 因 , 団
+4 Strokes
囧 , 困 , 囲 , 図
+5 Strokes
固 , 国
+7 Strokes
圃
+8 Strokes
國-->国 , 圏<--圈
+10 Strokes
園