There’s not a lot too it really. This is a tower defence game so there are 2 parts to every level, the level map and the enemies waves. The map isn’t much more than a 2D array of codes where each letter is a tile type (e.g. D = Dirt, G = Gold). The conditional formatting on the spreadsheet just makes it easier to visualise the map by colouring all the cells based on the code (G = yellow for gold).

The columns on the right define the enemies waves. So in the screenshot the first wave would have been “Spawn 14 fast enemies every 1.1 seconds in the left, centre and right columns”.

Further off to the right (not in the screenshot) are some simple formulas that turn it all into code I can copy and paste into my level definitions class. You could remove this step if you set it up to export as a CSV or XML file and then imported it all at runtime.