Revert "Revert 7d9bb30..7cc082f"

This reverts commit b7394afe2a40b96572810ff56ada634f82e5b91e.

	modified:   core.md
Revert "Revert "add demo url""

This reverts commit 7cc082f643a7edd1633a9687d36f68c24e72c09b.

	modified:   core.md
Revert "add demo url"

This reverts commit 7d9bb303efcbc7da774b124c20ec4d9260adf34e.

	modified:   core.md