Let's check it out!
Note: all Lil Evel Knievel development is based on devkitSMS Programming Setup and Programming Sample.
Download source code here.
|
|
|
|
|
|
|
|
|
|
Instructions
Lil Evel Knievel V1.0 game play is very open and simple due to the aggressive coding competition deadline: jump over varying platform gaps and pull off cool skateboard flips and trick combos to complete each level.
There are four jump categories on ground: Skip, Jump, Leap, Hurl. Once airborne, Lil EK can swap direction or flip somersault. Move opposite direction while airborne inverts somersault and down to accelerate land.
| Jump Categories On Ground | |||
| SKIP | Smallest | Left + Fire1 | |
| JUMP | Standard | Left + Fire2 | OR Fire1 |
| LEAP | Sizeable | Right + Fire1 | OR Fire2 |
| HURL | Colossal | Right + Fire2 | |
| Jump Activities Airborne! | |||
| SWAP | Direction | Fire1 | |
| FLIP | Somersault | Fire2 | |
Tools
Here is a list of Tools and frameworks that were used in the development of this project:
| KEY | VALUE |
| Programming | devkitSMS |
| Compiler | sdcc 4.1.0 |
| Assembler | WLA-DX |
| IDE | Visual Studio 2015 / Visual Studio Code |
| Languages | C / Z80 |
| Graphics | BMP2Tile 0.43 / GIMP 2 / paint.net |
| Music | pcmenc / vgm2psg |
| Emulators | Emulicious / Fusion / Meka |
| Debugger | Emulicious Debugger |
ROM Hacking
You can hack this ROM! Download and dump Lil Evel Knievel into Hex Editor, e.g. HxD, and modify bytes:
| ADDRESS | VARIABLE | DESCRIPTION |
| 0x004F | Delay | Used to speed through any game delay. |
| 0x0050 | Invincible | Non-zero value enables invincibility. |
| 0x0051 | Gravity Jump | Jump once while falling from gravity. |
| 0x0052 | HarderLands | Tougher platform collision detection. |
| 0x0053 | Music Off | Set 0=Music to play otherwise silent. |
| 0x0054 | Sound Off | Set 0=Sound to play otherwise silent. |
| 0x0055 | Riffs Off | Set 0=Riffs to play otherwise silent. |
Hints
- Four difficulty options: Easier, Normal, Harder, Insane. Difficulty increase = Visibility descreases
- Watch out for repetitive single turtles mixed in platforms as this can indicate large Leap or Hurl
- Favour Hurl for medium sized gap with opposite move direction to land inverted somersault OK
- Leverage down action on descent to land especially if you start to overshoot the target platform
Audio
Lil Evel Knievel includes digitized sound extensively by leveraging the pcmenc tool and uses development techniques outlined in devkitSMS Programming Sample under PCM Samples section. Some riffs you may have missed include: AC/DC, Austin Powers, Gn'R, Simpsons, Van Halen, Wayne's World, WWF Wrestling.
Music is often easy to neglect in a time pressure coding competition but Lil EK has been quoted as having "perhaps the single most impressive audo soundtrack the little PSG has ever seen".
Commands
The Command design pattern encapsulates a command request as an object. In game code, an example of a command request could be a move command: e.g. move sprite left, right or jump command flip, swap etc.
Coindentally, Lil EK uses 8x commands therefore each command stored as single bit mask; all 8x commands stored within a single byte. This way, combos can be bitwised detected rather than flattened out individually.
|
#define COMMAND_LEFT_MASK 0b00000001 #define COMMAND_MIDD_MASK 0b00000010 #define COMMAND_RGHT_MASK 0b00000100 #define COMMAND_HIGH_MASK 0b00001000 |
#define COMMAND_DOWN_MASK 0b00010000 #define COMMAND_JUMP_MASK 0b00100000 #define COMMAND_SWAP_MASK 0b01000000 #define COMMAND_FLIP_MASK 0b10000000 |
Critical to the development process, streams commands can be issued to the game engine for debugging all possible game play scenarios. Plus commands can be recorded for playback to show case instructional demo!
Physics
Game physics are aptly based on the "The Motorcycle Daredevil" projectile motion practice problem. Here are player angle / speed combinations to produce four jump types nicknamed Skip, Jump, Leap and Hurl.
| Type | Angle | Speed | Horizontal | Vertical | Max Frames |
| SKIP | 45 | 30 | 92 | 23 | 53 |
| JUMP | 45 | 40 | 163 | 41 | 81 |
| LEAP | 45 | 55 | 309 | 77 | 133 |
| HURL | 40 | 65 | 425 | 89 | 177 |
Sprites
The Title screen uses Zoom sprites in which the 24x32 player sprite is magnified as a 48x64 sprite. However, SMS I has a bug in how the VDP processes zoomed sprites. Therefore, to circumvent the VDP bug you have to draw 4x additional sprites on the same Y coordinates of the original sprites as seen in title_screen.c file.
YouTube
YouTube videos showcasing all SMS Power! 2023 coding competition entries including some with long play:
| TITLE | AUTHOR |
| New Master System Games for 2023 | Dudley of Yesterzine |
| The Ultimate SMS Coding Showdown | CrossGenGameplay |
| Présentation SMS Power Competition | Révo SEGA 8-bit |
| Master System Game Lil Evel Knievel | Genesis 8:14 |
Summary
There has been progressive interest in Sega Master System Homebrew as coding competition entries become more impressive. Unfortunately due to time constraints, the game mechanics and level design were not able to be fully developed at this time. However the foundation for potential future development did receive some incredible feedback from the community and Sega 8-bit preservation and fanaticism fans. That is awesome!
No comments:
Post a Comment