Let's make a piano

Ultima Online is now 10 years old and I stumbled upon this post by Damion Schubert. He describes some unplanned uses of the game that gave a "magical" touch to UO.

My attention has been caught by how players found a way to build a piano by using shirts and a chess board. While I never played UO myself, I've seen similar creativity in SWG. In fact, some players dedicate quite some time just to build stuff that wasn't planned in the game. All of this comes down to players' freedom and I realized how I could a bit more freedom in my project.

I use a very rigid x,y coordinates system when it comes down to deal with items positions. You have to see it as a grid and all items are contained in a cell (or more if they're bigger but their positions are relative to the cells). So if I want to see a player made piano in my game one day, I'm not helping players here by restricting how items are shown.

By now, it seems pretty clear that my game will be all javascript and CSS, Flash being just too expensive for my wallet and learning it could be a good way to never see the end of this project. When an item is displayed, I received coordinates from 1 to 15 horizontal and 1 to 10 vertical (just the current size I'm using, this could change). I multiply the coordinate by 50 (cells are 50x50 pixels) and there I have where the item will be displayed. What if I could add an offset notion?

I created a new table containing offsets for each items. The values contained in this table are pixels. This way, I pass the coordinates of each object to the client with the offset. The pixel position is calculated and then I apply the offset, allowing items to be placed wherever the player want it to be. With the pixels offsets, I added an offset for the Z-Index that will affect on which layer the item will be shown.

Players will use the /offset command to change those values. To move a chest 30 pixels to the left, just type /offset x -30 and the chest will appear 30 pixels to the left. Of course, not all items will be allowed to be moved like this. Only items with no elevation (no collision) will be allowed to be moved this way to prevent any abusing.

There it is, a way to build a piano! Not the kind of thing that was part of my priorities list but considering how little time it took me to code, it was well worth it for the possibilities this might open.