Collectible Card Game Headquarters

I have Mac OSX Version 10.6.8.
I have done a test in Safari that shows I am running Java.

I clicked on forge.command and get this error from terminal
Exception in thread "main" java.lang.UnsupportedClassVersionError: forge/view/Main : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
logout

[Process completed]

Please help guide me through the mac install process!
thanks much!

Recent versions of Forge require Java 7 and your computer is limited to Java 6. See number 12 in the Forge Frequently Asked Questions topic.