Encrypted mixed media data (201) may be read by many browsers (101) from a server (108). Downloaded encrypted environment data includes data modification access codes. A user access code is received and an access check (214) is performed against the decrypted environment data (213). The user access code is processed in combination with the data modification access codes to determine an extent to which a user is permitted to view, modify or interact with the environment data under the control of a data modification process (215). Animation data (202 to 209) is received and animation data is rendered (217) whereafter the rendered data is displayed (218).