1. A computer program product, tangibly embodied in a machine-readable medium, the computer program product comprising instructions that, when read by a machine, operate to cause data processing apparatus to: determine a position of an avatar in a user interface; dynamically define a curved guide line to surround at least a portion of the determined position of the avatar, wherein a starting point and an ending point of the guide line are aligned vertically, further comprising: determining a range of motion of an arm of the avatar, and defining the guide line within the range of motion of the arm; display, without obscuring the avatar, alphanumeric characters aligned with the guide line; receive a cursor-based user selection of one of the displayed alphanumeric characters; animate the arm of the avatar based on the cursor-based user selection; and highlight, based on receiving the selection, the selected alphanumeric characters, further comprising: increasing a size of the selected alphanumeric character to a first extent, and increasing a size of an alphanumeric characters on each side of the selected alphanumeric character to a second extent less than the first extent.