GameDev Tutorial - Creating a Simple Game

Step 1 - Creating Graphics

The tileset editor within GameDev opens a full screen display in order to ensure the desired color depth for the images. This may make it difficult to follow this tutorial on-screen, so before beginning you may wish to print this page out for reference as you proceed with this first step of the tutorial. However, if that's not an option, GameDev does allow you to Alt-Tab between the full-screen display and the desktop.

From the main project view in GameDev, all areas of the program can be accessed via the View menu. We want to start out editing Tilesets. Tilesets store the graphics for all the tiles and sprites. Select "Tilesets" from the view menu and the Edit Tilesets dialog will appear.

From the Edit Tilesets dialog you can create new Tilesets, create Tilesets based on existing images, import pieces of other images into a Tileset and manage tilesets in other ways. Right now we want to create a new Tileset, but first we need to specify some parameters for the tileset.

Note: GameDev imposes a maximum of 256 tiles per tileset. This is because each layer only uses one byte per tile and one byte can't represent a range of more than 256 tiles. If you need to represent more graphics, may I recommend adding layers with different tilesets. The optimal tileset size (when using 32x32-pixel tiles) is 512x512 pixels (16x16 tiles) if you want to get the maximum number of tiles in the tileset.

If you want to skip this step and use graphics already prepared for the tutorial, you can click the "Load Image" button and load Tutorial.bmp which contains the graphics we will be creating in this step.

Before clicking the create button, note the selection for screen depth at the bottom of the window. This is not a setting saved with the tileset, but is an option for how to open the full-screen display to begin the tile editor. It can, however, affect the format of the tileset. For this tutorial, let's leave the selection at 16-bit color. Some video cards do not support 24-bit color or 32-bit color. Editing a tileset in 16-bit color mode will reduce the format of the graphics to 16-bit color. Be careful if you load a 24-bit color image into a 16-bit color editor, some color information can be permanently lost. After noting the screen color depth, click Create.

After clicking the Create button the full screen tile editor is presented.

The first thing we should do is click the button that reads "Make 16-bit". This forces all colors in the color palette to map exactly to a 16-bit color. If this is not done, a flood fill may fill an area with a dithered color. The change is imperceptible (at least to me) but if you start filling and re-fillling areas with inexact colors, you will see the problem.

Lets start with some very basic graphics that we can use to draw tiles on the map, and later on, to include in our sprite definitions. We'll start with a tile representing a solid chunk of steel. The fifth color from the left on the bottom row of the palette looks like a good steel grey. Left click on this color, then click the "Solid rectangle" button. Drag the mouse from coordinate 0,0 to 31,31 - that should result in a grey rectangle accross the whole grid. (Mouse coordinates can be seen directly below the grid on the left side.)

When drawing graphics onto the tile editor, the mouse can be clicked on either the grid with the magnified view of the tile, or on the tile graphic itself, to the right of the grid at the top. These areas represent the tile in memory that has not been stored into the tileset... consider it a working area for the tile graphic.

Now let's add some shinyness/irregularity to the "steel surface". The eighth color from the end of the palette looks like a good steel blue. Select this and then click the line button. Draw some parallel diagonal lines on the gray tile. Try some white lines too (the last color). Draw the lines at a 45 degree angle to the edge for reasons we'll see later.

It looks a little pixeled, let's try to fix that. Click the "Smooth" button and drag a rectangle over the entire grid (just as was done for the grey rectangle). Viola, automatic pixel blurring (almost as good as anti-aliasing).

Good enough, let's store this tile in the Tileset. When the tile editor first comes up, the very first tile in the Tileset is selected by default. We don't want to store the tile in the first "slot" because this is the tile used as the background when drawing the map (tile zero). Since we're going to stick with a black background right now, select the next tile. To do this, click the right arrow (">") button below the grid or click on the next tile in the tileset window near the bottom right. Store the tile into that slot by clicking the "Store" button below the grid.

If you want to draw a second similar tile (this might be good so that not all solid metal looks exactly the same) click the clear button and repeat the process starting with the gray rectangle. Store the resulting tile into another empty slot in the tileset.

The tile(s) you have just drawn will be the center of a number of tiles that we will use on the map to construct larger structures. Now we need to define some edge pieces that can be put around this tile to make it blend nicely with the background. Let's start with a block for the top edge and we'll move on from there.

To make the edge pieces we will fade the steel gray to a darker shadowed color, and at the very edge have a solid bright surface. Let's create our own shadowed color in the palette. Pick a color that we haven't used (with a left mouse click on the palette). Now use the R++, R+, R-, R--, G++, G- (etc.) buttons to adjust the components of that color. Get something around R=20, G=20, B=40.

To make a smooth gradient from the shadowed grey to steel grey, click the vertical gradient button. It's possible to make gradients in the palette itself, but we don't need to because we're drawing a simple vertical gradient rectangle. Now select the colors for the gradient: left-click on the shadowed grey and right-click on the steel grey. Drag a rectangle (left mouse button) on the grid that covers the whole tile. This should result in a smooth gradient with the shadowed color at the top and the lighter steel grey at the bottom.

Draw some of the same diagonal lines that we drew for the center block, but confine them mainly to the lower half of this tile. Also, perform the same smooth operation afterwards. (Don't forget to select the proper tools before drawing on the grid.)

Now we need to add the solid edge on top. A shorter gradient to white should do the trick. Left click on white and right click on the shadowed color. Click the vertical gradient button and draw a 4-pixel-high rectangle accross the top of the tile. This tile is done! Store it to a blank slot in the tileset and we'll move on.

When drawing gradient rectangles, the color selected with the mouse button always goes on the corner where the drag was started. If you use the right mouse button to drag, the color selected with the right mouse button goes at that corner.

This edge tile can be easily manipulated to quickly make the tiles for all the edges. In the process you'll learn how to use the rotate and flip commands.

Click the Copy button. The flip and rotate commands only operate on the copied clip of graphics, not directly on the tile. Select the whole tile (drag accross the whole grid). Now the whole tile has been copied into the tile editor's "clipboard" (which is not the system clipboard).

To make the tile for the right edge, click the "Right 15" button until the rotation is at -90 degrees. The tile is facing the right direction now, but the diagonal lines are going the wrong direction. Now since the lines were drawn at a 45 degree angle there's a simple solution to this. Click the X Flip button to flip the copied clip horizontally. Now when we paste the clip the diagonal lines will be going in the right direction. Click the "Paste+" button. This is the tool used to paste the clip when it is rotated (Paste will paste exactly what you see under "Clip").

As you move the mouse pointer over the grid you will see the clip draw in it's rotated orientation, centered around the mouse pointer. Move the pointer until the rotated clip covers all the pixels on the grid, then click the left mouse button. You now have a tile for the right edge. Store this tile into a blank slot in the tileset.

Now continue to rotate and flip the tile in various ways until you have a tile for all the flat edges (left, right, top, bottom). Store each of these into the tileset.

The corner tiles will take a bit more effort. To get us started, load the tile for the top edge. We're going to need one column of pixels that contains the exact gradient used in the edge tiles. If your diagonal lines (or their smoothed pixels) have affected the edges of this tile, avoid these edges in the following steps (You may need to re-create the gradient without diagonal lines if both edges of your gradient were affected by the diagonal lines).

Copy one column of pixels by clicking the copy button and dragging from the top of the tile to the bottom of the tile without enclosing more that one column width of pixels. Be sure to do this on a column of pixels that has not been affected by the diagonal lines. This column of pixels will be used as a pattern to reproduce the gradient diagonally.

Now click the clear button to clear out the grid to prepare for a new tile. Paste the column of pixels along the left side of the of the new tile so it extends from the top to the bottom of the leftmost column of pixels in the tile. Now use the rotate buttons to set the rotation to -90 degrees (right 90 degrees). Click on Paste+ and paste the one row of pixels along the bottom of the tile. There should be one pixel where the two paste operations intersect at the bottom left corner and the color of that pixel should be the same in both.

Now that the edges are set up to match neighboring tiles, we'll fill in the rest. This tile will be a sloped tile to fill in the top right corner of a block of steel tiles. The slope will extent from the top left corner to the bottom right, filled in on the bottom left half of the tile. The easiest way to do this is to click the "Make R. Button Pick" button and then click the line button to start drawing lines. Note that when you now right-click on the grid, the color at that pixel will be assigned to the currently selected color in the palette (primary selection). So be sure the currently selected color is not an important color. If you do lose an important color, you can click the Reset button to re-initialize the color palette. Remember to click "Make 16-bit" again.

Right-click the top-leftmost pixel of the tile (white) then left click and drag down to the bottom-rightmost pixel. Right-click on the pixel to the left (30,31) then click and drag to 0,1. Right-click on 0,2 then click and drag to 29,31. Continue this process until the lower left half of the tile is completely filled in. Store the new tile into a blank slot in the tileset.

Before adding any diagonal lines to this image, we should rotate/flip it in all directions to get the 4 corner pieces we will need (If you add the diagonal lines too soon, the tile will only be usable for two corners instead of four, if you want all the diagonal lines to be parallel). So flip and rotate as necessary and store all 4 corner pieces into the tileset. After this is done you may wish to go add diagonal lines to them. Be careful not to smooth any area beyond the white edge or the white will smear into the black.

Only 6 more tiles are necessary for a complete set of tiles that can be used to make any shape. Currently we only have the tiles necessary for a convex shape. To allow concave shapes we need inner corners. Copy the same column of pixels used in the previous section on making the sloped tiles. However, this time the top pixel (white) should be excluded from the copy, resulting in a 31-pixel column instead of a 32-pixel column. This is done because in a series of sloped tiles, the neighboring exterior tiles will contain the white pixels while this new tile resides entirely on the interior. Paste the copied graphic at the top of the leftmost column of a blank tile, as before, but this time, rotate it the other direction and paste the second image (horizontal row of pixels) along the top so the 2 lightest-grey pixels overlap.

The bottom-most pixel and right-most pixels should be copied from the neighboring pixel. Since there were only 31 pixels in the copied graphic, the bottom and right would be black, but we want it to be grey. This can be accomplished by pasting each version of the graphic twice: for instance, paste the graphic at 0,1 before pasting at 0,0.

Now connect the edges with diagonal lines like before. Right-click on the bottom-leftmost pixel, then click and drag to the top-rightmost pixel. Then right-click on 30,0 and click and drag to 0,30. Right click on 0,29, then click and drag to 29,0. Repeat until the upper left half of the tile is completely filled. Store the tile when complete and KEEP this copy of the tile as is because we will need it for the last 2 tiles. Now fill the lower right half of the tile with the steel gray color. This is actually the tile that we will use on the map. Rotate it 4 directions and store it, add diagonal lines and smooth if you wish.

The two remaining tiles apply when two 2-by-2 blocks of tiles overlap at their corners. Load the tile that was stored to "KEEP" in the previous step. It should be noted here that "Paste+" treats a color as the transparent color if it appears in all 4 corners of the copies clip.

This being said, we want to have a transparent color - we'll want to make all 4 corners black. Left-click an unused color in the palette and (assuming R. Button Pick is turned on) right-click the lightest grey pixel at the top left corner (this pixel represents the area closest to the exterior edge of the tile). We need to remember that color for later. Now put a black pixel in each corner of the tile currently loaded into the grid. Then copy the entire tile into the "clipboard" with the copy button (and then dragging over the whole grid). Now set the rotation to 180 degrees and click on Paste+. You should see when you move the mouse over the grid that the triangle fits nicely into the empty half of the tile without disturbing the half of the tile already there. Match it up so the whole tile is full (except the corners) and click to paste. Select the previously stored color from the palette, select the "Pixel" button and put the light grey pixels back on the exterior corners (there are now two of them). Then select the steel grey color from the color palette and click the two steel grey pixels into place in the other two corners.

Store the tile into the tileset, copy it into the clipboard, flip it, paste it and store this one too, and you're done! These are all the tiles necessary to create a complete TileMatch definition.

Sprite Graphics

We have the tiles we need for the the basic framework of the map, but it won't be very interesting without something else to put on the map. The most fun type of sprite to make is one that turns is all directions (well, 36 directions feels like all directions anyway). For this we need 36 consecutive blank tiles. There's not enough room in the tileset to store these tiles right now. So this is a good time to demonstrate the "Update" command on the tileset.

Close the tileset editor with the close button. This would also be a good time to save what you've done so far. After closing the full screen editor, click the tileset name in the list (the "[L]" means it's currently loaded into memory). Click the Save button and specify a path and filename for the BMP file.

Now click the tileset name (if it's not already selected) and increase the number of rows from 4 to 8. Then click the Update button. The screen will flip into full screen mode momentarily while the graphics are manipulated on a full screen display. If you select the tileset and click the Edit button to return to the editor now, you will see there are 4 new rows of blank tiles. This is enough to create a 36-state rotating sprite.

Let's create a simple spaceship type graphic. It should be pointing to the right because when we define the sprite using the graphic, the automatic sprite frame assignment starts at zero degrees (which corresponds to something pointing to the right).

My ship was composed entirely of ellipses. The entire ship should be constrained to a few pixels from the edge, even more near the corners. The reason for this has to do with rotation. When the image is rotated 45 degrees, the rotated image must also fit inside the same square. So if you want to make a ship shaped exactly like mine, here are my parameters

Store this image of the ship into the tileset in a blank slot. Choose a slot on a row that doesn't have any other images. The automatic rotation process will store rotated image in the 35 cells following the current cell, overwriting anything that may already be contained in them.

Click the "Turn AA On" to turn Anti-Aliasing on. If the button reads "Turn AA Off" then Anti-Aliasing is already turned on. Then click the "Make 360/10" button. Watch as the original tile is rotated to 35 other consecutive orientations and stored into the tileset.


Notice that the images that didn't fall exactly at a multiple of 90 degrees are a bit blurred by the anti-aliasing and don't quite match the images that are at exactly 90-degree increments. To make all the images look more uniform let's smooth the images that still have sharp edges. For each ship image in the tileset that has the sharp edges (there should be 4) do the following:

Those are all the graphics we need for our sprite. Just a little more left before the tileset's done.

Inventory Graphics

Generally a single graphic can be used both to represent an item on the map as well as in the inventory. We're going to create two simple tiles to represent items the player can pick up and own.

Your artwork may be better than mine here so feel free to improvise. The first item I wanted to represent was a "scraper". This is something that can be used to "scrape" away walls. I used the pencil tool to draw a sharpened-looking "tool" onto a representation of the front of the ship. Then I used the smooth tool to pretend it didn't look so bad. You may wish to draw something more drill-like.

The second item is some sort of staff. I drew the base and the ball separately, smoothed them, then joined them together by transparently pasting the base over the ball using Paste+. Some near-black pixels had to be removed after smoothing (before copying) for this to look good. Remember all four corners of a copied graphic must be exactly the same color in order for Paste+ to pick a transparent color.

These two tiles should be stored into two blank slots in the tileset. There should be plenty remaining.

These are all the graphics we need for our basic tutorial. Click the close button, select the tileset in the list of tilesets in the "Edit Tilesets" window and click the "Save Image" button. Specify the name of the same bitmap used earlier and save our completed Tutorial tileset.

This concludes Step 1 of the GameDev tutorial - Creating Graphics.

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