1. A method comprising: displaying, by a computing device, in a graphical user interface a design canvas area, wherein the design canvas area includes a plurality of placed blocks arranged by a user to specify a definition for a trading algorithm; receiving, by the computing device, a change command from the user via the graphical user interface to change the arrangement of the plurality of placed blocks; detecting, by the computing device, the change in the arrangement of the plurality of placed blocks, wherein the change in the arrangement of the plurality of placed blocks includes a change with respect to a changed block; determining, by the computing device, whether the trading algorithm complies with a trading algorithm rule based on the detected change in the arrangement of the plurality of placed blocks, wherein the trading algorithm rule defines a problem associated with a block type of the changed block; displaying, by the computing device, in the design canvas area of the graphical user interface a box around a portion of the plurality of placed blocks when the trading algorithm does not comply with the trading algorithm rule, wherein the portion of the plurality of placed blocks are the blocks that do not comply with the trading algorithm rule; receiving, by the computing device, a selection command from the user via the graphical user interface selecting the displayed box; and displaying, by the computing device, in response to receiving the selection command, in the design canvas area of the graphical user interface the box with an opaque background, wherein the opaque background is behind the portion of the plurality of placed blocks and obscures the remaining blocks in the plurality of placed blocks.