The isometric line
Isometric is my favorite genre, and it starts with one simple pattern. An isometric line goes two pixels across, then one up, then two across, one up, and so on. One, two, one, two. If you remember the rule about smooth lines from the outlines lesson, this is it: a steady rhythm, so the line looks straight.
Before you draw anything else, practice that line. Draw short pieces first, then longer ones as you get confident. Then build a cube: draw a square, a second one below it, connect them, erase the inner edges so the cube isn't transparent, and give each side its own shade. Make five or ten cubes. Your brain will feel twisted at first. That's normal, and it passes.
Step 1: Outline
Start with an isometric line of 15 pixels and a short one of 4 for the side. Copy them, flip them, and place them on top to close the top face, leaving one pixel of space at the corners. Copy the lines again 11 pixels down for the bottom, connect top and bottom, and erase the inner edges.
Then the fan hole on the front: find the second step from the edge, count three pixels, and start the hole on the fourth. Add the slots on the front and the side the same way, by counting pixels.
Step 2: Colors
Fill the box with the main grey. I like to keep every step on its own layer here: outlines, colors, shading, highlights, details. You can also do it all on one layer.
Step 3: Shading
The light comes from the top front. So the right side is in shade, and the top gets a light touch of shade too. The back wall is almost completely dark, and so is the inside of the fan hole. Darken the slots, then use a slightly lighter grey to give the hole some depth.
Steps 4 and 5: Highlights and details
One line of the lightest grey along the top front edge, where the light hits. Then a few pixels of texture in the side slots. Done.
This little machine is one piece of a whole isometric building in the course: arcade rooms, balconies, signs, a rooftop. Every one of those starts as a box like this.