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In part 4, I put together the foundations for a mini shooting game, with targets moving on the screen and you can ‘hit’ them by clicking inside the targets, etc. etc. I promised an update to make it feel more like a game, so here it is!
Adding a background
The black background was more than a little dull so I had a look around for some freely available images, and to apply them I had two simple choices:
- draw the image onto the main canvas on each frame
- use the image as background to the canvas
I opted for the latter as it seems more efficient, it does mean that I need to change the way I’m clearing the canvas for each frame though. In part 1 of this series I mentioned that by setting the width or height of the canvas element you can erase the contents and reset all the properties of its drawing context, which seems to fit the bill of what I’m trying to do here.
The clear function is therefore changed to:
Limit the number of Shots
To make the game more challenging (having an unlimited number of shots is just too easy), I decided to add a limit on the number of shots you can have and after you’ve used up all of them it’s effectively game over.
To show how many shots you have left, I want to show a number of bullets in the top left corner and depending on the number of shots you have left the bullets are shown differently:
- Five shots or less and you will see a bullet for each
- More than five shots and you will see a bullet followed by the words x N where N is the number of shots left
- If no restriction on the number of shots (for time attack mode for instance), you see an infinity sign next to a bullet
To facilitate these requirements, I need to be able to track the number of shots left and decrement its value every time you click inside the canvas element. Thankfully, the structure is there already, just need some small modifications:
Then I need to take care of the business of actually showing them on the screen, luckily it wasn’t too hard to create a basic bullet looking image and an infinity symbol. To make it easier to use them over and over in my code, I added two <img> elements to the HTML (along with a third which I will explain later) but they’ll be hidden:
And these are the results:
Looks the part, if I might say so myself :-)
Using a Custom Cursor
Though a good approximate, the crosshair cursor just isn’t quite up to the task here, a scope-like cursor is needed here, like the one I created here:
(if you’re interested in how I made the cursor, I used Axialis CursorWorkshop which makes the task simple)
All that’s left is to replace the crosshair cursor in CSS, but still keeping it as fallback:
A similar change needs to be applied to the HTML:
After that you’ll start seeing the new cursor when you run the game.
Adding a Bullet Target
Thanks to my wife Yinan for giving me the idea of having bonus targets which are harder to hit but give you extra bullets when they’re hit. You have already seen the HTML changes earlier, and probably noticed that I have switched to using an image rather than drawing the regular target boards by hand..
The logic of removing a target from the targets array is now moved out of the Target class and the code which generates targets during initialization has also changed to generate a bullet target by a configurable chance:
The full demo can be found here, hope you like it, I’ll be adding even more features in the near future so come back later if you’re interested in seeing how far this little game can go!
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Here is a complete list of all my posts on serverless and AWS Lambda. In the meantime, here are a few of my most popular blog posts.
- Lambda optimization tip – enable HTTP keep-alive
- You are wrong about serverless and vendor lock-in
- You are thinking about serverless costs all wrong
- Just how expensive is the full AWS SDK?
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- We can do better than percentile latencies
- Yubl’s road to Serverless
- AWS Lambda – should you have few monolithic functions or many single-purposed functions?
- AWS Lambda – compare coldstart time with different languages, memory and code sizes
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