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Building iPhone Apps: From Flash Lite to Corona
1. Building iPhone Apps:
From Flash Lite to Ansca Corona
Evan Kirchhoff, Comrade Software
September 30, 2009
(Notes are exported here)
2. - Comrade Software - founded in 2002, doing mobile Flash since Summer 2002 (PocketPC)
- Contract Web games, internal mobile games
- Also games released on Verizon (USA) and Softbank (Japan) via publisher Smashing Ideas
- But mobile Flash is difficult to monetize...
6. ‣ Uses the Lua language: easy lateral shift from
Actionscript
‣ Existing Flash assets and program logic can
often be re-used, or ported rapidly
‣ Development time comparable to Flash,
shorter than iPhone SDK, much shorter than
OpenGL
8. Problem #1: Carriers
- To develop Flash for Verizon, we had to join the BREW developer program at $400/yr to
code-sign on test phones
- NSTL testing fees were $800 per application per device model (14 phones total) = $11,000,
paid by publisher
- Testing process much more finicky than Apple’s; some games from other developers failed
at least once and publisher had to pay test fees again
- Standard breakdown: carrier takes 50% of revenues, publisher takes 50% of remainder
9. Problem #2: Fragmentation
- Flash addresses the fragmentation problem with rescaling (much better than the 6-figure
porting costs for wide-released mobile Java games), but you still end up compromising
design to ship a unified binary, due to the range of target devices
- Apple avoids this problem by only making one device, more or less
13. - This is a Comrade-built native SDK app (because we needed MapKit), but note how most of
the onscreen elements are still custom bitmap graphics, including all buttons and picker
wheel “highlight” bar
- As it happens, most of the graphics were created in Flash
14. When to use Corona?
‣ 2-D games
‣ Graphically-oriented utilities
‣ Rapid prototyping
‣ Adware, presentations, promotional items
(cont’d from previous slide)
15. (Example of adware in the App Store)
- Currently not for apps with Apple-style UI controls, although UI features have been
requested
- Currently no 3-D (or Flash-style “2.5-D”) support; also requested
16. The Corona Development
Environment
‣ All application code in “main.lua”
‣ All assets in directory are compiled into app
‣ Good (free) text editor:
www.barebones.com/products/textwrangler
(URLs will be repeated on last slide)
19. (Other Lua books -- note that Lua tends to be used as a game-development language)
20. Basic Lua Syntax in 60 Seconds
Actionscript:
Lua:
- Will feel similar to Actionscript, but adds “do”, “then”, “end”, etc.
- Semicolons at ends of lines are optional
- Need to break the habit of using curly braces for code blocks
21. Tables are Fundamental
- Curly brackets are reserved for declaring tables
- Tables are the fundamental object in Lua; tables = associative arrays (or dictionaries)
- Functions are first-class variables, and you can redefine any function anytime (including
sin(x))
- Lua is not heavily object-oriented by default, and the PIL book discourages encapsulation.
However, it is possible to build your own classes and objects -- see PIL, and brief discussion
at end of this talk
22. Think Locally
Bad: Good:
(30% performance difference)
- A major Lua optimization is using local variables (and functions) only
- Declaring a local copy of the sin function means that it doesn’t require a lookup from the
global “math” table
23. More Familiar Objects
Flash:
Corona:
- Other similar elements include event listeners and transition libraries
- Notice less code coloring in the 2nd example; this is because TextWrangler doesn’t know
how to color the Corona framework objects (this would be a nice-to-have feature)
24. Our Friend, the Button
- Corona example code includes a robust button object (handles rollout correctly, etc.)
25. Flash Lite Conversion #1:
Poker Arcade
- A collection of 6 popular video poker games; Flash version completed in 2007
26. - Game originally developed in FlashLite 1.1 (no functions, no arrays, etc.) for maximum
device compatibility
- Card assets (the most time-consuming to create) taken directly from Flash to Corona, using
PNG export
27. - Main program logic (dominated by lengthy scoring routines, especially in Deuces Wild)
ported with very few changes; new code mostly involved the UI.
- Game was playable within a couple of days; total coding time was less than a week
28. - The single biggest step was the creation of new background and UI assets to take
advantage of the large screen (graphical production time exceeded coding time)
- Making the higher-res graphics took another week, so total development time was about 2
weeks
31. - Final build has about 2000 lines of code
- Particle effect added for win animation: a burst of stars falling under “gravity”
- Surprising number of stars could be animated, compared to many mobile Flash devices (I
was hoping for 3-5)
- The game came out well, but the source code is another matter...
32. The Poker Arcade Design Pattern:
We’re happy with how the game turned out, but I would organize the code much differently if
doing it again...
33. Poker Arcade: Lessons Learned
‣ The Flash timeline had hidden the spaghetti
logic of the original program
‣ But Lua functions and variables declared
“local” are sensitive to code-ordering...
‣ ...which led to declaring everything as global...
‣ ...which caused memory management issues.
‣ Eventually, brute force was used: load all assets
at once; never deallocate or reallocate
anything ever.
(This approach is not recommended!)
35. (This slide is a 60-second embedded video demo)
- Flash version completed in 2007
- Based on Breakout (1976), but using polar coordinates rather than (x,y), and circular
wraparound
36. 150 kb limit,
8-10 fps on Motorola RAZR
- Limited to 150k by Verizon
- Lowest-common-denominator device (and most common) was Motorola RAZR.
- Performance in Flash on RAZR was 8-10 frames per second
- All assets had to have simple vector shapes (optimized repeatedly in Flash)
- On low-end phones, bitmaps are faster than vector, but this uses up the filesize limit
rapidly
37. - For iPhone version, since the screen is much bigger (and user expectations higher), much
more graphical detail was added
- Some Flash assets resized and re-used; others redrawn
- We also decided to make it a tilt-controlled game, and went to a landscape orientation
- In score field, “LED” style replaced with “Nixie tube” style
38. (Detail comparison)
- Since all assets on iPhone are bitmaps, and there’s lots of memory, there is no reason not
to use subtle shading, shadows, glow effects, and other details
39. - Same level designs ported directly from Flash version
41. Core Damage: Lessons Learned
‣ Use object-oriented principles for code
organization
‣ Most importantly: forward declaration allows
sensible code ordering while maintaining local
scope throughout
‣ Better use of reusable objects
‣ “Movieclip”-like objects created to replicate
advantages of Flash
‣ With fully-bitmapped assets, detailed visuals
are “free”
42. My Corona Wish List
‣ A mechanism for “includes” or external
libraries
‣ Specialized game-dev support (e.g., physics
engine?)
‣ Tethering iPhone to simulator for
accelerometer testing
‣ Local peer-to-peer networking support
‣ 3-D support
‣ Keyboard and other UI controls
