This run aims to complete Sonic CD as fast as possible using various tricks and glitches. This also improves upon the current publication by 14"24 in-game seconds, or 824 frames.
Game objectives
- Complete the game as fast as possible
- Optimize for both In-Game Time (IGT) and real-time
Comments
Sonic the Hedgehog CD (commonly called Sonic CD) was a game released in 1993 for the Mega CD/Sega CD addon for the Sega Genesis. This game is infamous for its unforgiving level design, however it is also known for its amazing music. There are two versions of the OST: one was used for the Japanese and European releases of the game, but for the American release they changed most of the soundtrack (the Past songs remain unchanged) to be "more rich and complex."
Sonic CD may be infamous for having some poor level design choices, however it also introduced several new characters and mechanics:
- Sonic CD introduced two new characters: a clingy pink hedgehog named Amy Rose, and the robotic antagonist known as Metal Sonic.
- Sonic CD removed the ground speed cap (however the speed cap in the air still exists) and also introduced a new ability for Sonic called the Super Peel-out. It also added the Spindash, although it does not work the same way we are used to. They are both very slow to charge, and since the peelout is actually faster to charge than the spindash, the peelout is used more often in the run.
Below is an explanation of a couple glitches used in the run:
Moving Peelout
The Moving Peelout (abbreviated to MPO) is a glitch where Sonic is able to move while charging a peelout. This can be accomplished by charging a peelout and pressing up, down, and a horizontal direction on the same frame. There is also an RTA-friendly method which can be done by pausing during a charge, letting go of up, holding down and forward and unpausing, pausing again and switching to up, and unpausing yet again. This causes Sonic to slide along the ground at the speed of the charged peelout. If that sounds confusing, then think of it as this: The longer you charge the peelout before you start an MPO, the faster you will slide on the ground. Not only does the MPO allow you to get a headstart when charging a peelout, it also allows you to go right through walls! When you are charging a peelout, the game is not checking for collision since you're not supposed to move when you're charging a peelout, but by performing an MPO you can perform a zip pretty much anywhere you want! This is happily abused throughout the run in various ways, whether it's to skip an entire level or just to save a couple of seconds.
Zips/Level Wraps
Zips occur when your character gets stuck inside of a wall and you press any horizontal direction. Depending on which direction you press, you will be sent the opposite direction. For example, you get in a wall and you want to go right. You don't want to press right to try to go right, because you will get sent left instead and end up escaping the wall. So if you press left, you'll go right and you'll get to your destination. When performing a zip going left, if you hit the left boundary of the level, you can perform what is called a "horizontal underflow," or a level wrap. Wrapping in certain levels can save time, but in some levels it's either a loss of time or doesn't allow you to finish the level, whether by being too high to reach the goal post or by just killing you.
This run in particular was performed on the Japanese version of the game, which has a couple differences from the American version:
- Score tallies in the Japanese version are about half a second faster than the American, due to the length of the level clear jingles differing between regions.
- A quote from the author's notes of marzojr's run:
The Japanese and US versions have a slightly different way of handling the in-game time and lag frames. The US version works like the other 2D Sonic games and only updates the in-game timer on non-lag frames; the Japanese version, however, appears to update the timer also when there are two consecutive lag frames.
Improvements Made
Here are the parts of the run that were improved:
Collision Chaos 1
Collision Chaos 1 features a level wrap right at the beginning of the level! After entering the wall, I adjusted marzojr's inputs in order to change my subpixels, which allows me to get a faster zip out of the wall. This ends up saving 0"23 IGT seconds! However, the risk for crashing the game is VERY high when doing this fast zip, so unless you know what you're doing and have a consistent setup, I would not recommend this.
Collision Chaos 2
Collision Chaos 2 had a level wrap discovered by RTA speedrunner Zaxon96, and it involves the following method:
- Start the level as normal, performing a high jump to reach the top of the level and go over the ceiling.
- After jumping on top of the level, jump back down to destroy a specific badnik, and land right after the second ledge.
- Perform an MPO into the ledge, and once inside the wall, perform a zip to the left.
Once you leave the wall, you need to jump at a specific point on the platform, and from there the trick becomes a subpixel nightmare, where I had to monkey around with holding right on different frames and jumping at different times, and eventually made it to the start of the level and wrapped, saving 2"77 IGT seconds!
Tidal Tempest 2
Much like CC2, Tidal Tempest 2 had a level wrap discovered by RTA speedrunner CubbyCat where instead of going below the moving blocks to continue the level, you instead jump on top of the leftmost block while it's coming out of the wall, and perform an MPO into the wall to fall down to another part of the wall. You have to wait for the water level to go down otherwise the trick won't work. You also have to tinker with subpixels here as well, since you have to get a full zip (not a half zip), AND you have to clip through TWO WALLS. Once you get through and wrap, this trick saves 10"88 IGT seconds! The reason we have to do the wrap in this specific way is if we just fall down to the part of the leftmost wall where we can zip, we end up being stuck in the ceiling above the signpost, and we're too high to be able to activate it, softlocking us.
Quartz Quadrant 1
Quartz Quadrant 1, like CC2 and TT2, had a level wrap discovered by Werster that involves abusing time travel in order to clip into the wall in the Bad Future version of the level. It's as simple as that, and it's an easy 0"35 IGT second save!
Metallic Madness 3
Metallic Madness 3 has no new tricks or glitches, but instead there's a timesave during the final boss. After hitting him for the third time, Robotnik will launch his last... slab? I don't know what it's called, so let's just go with "projectile." Anyways, after hitting him the third time, this projectile will home in on where you're standing to try to hit you. It turns out that by standing at EXACTLY X position 3840 in the middle of the screen, the projectile Robotnik launches at you hits the ground as soon as possible, which saves 0"27 IGT seconds.
In-Game Completion Times vs. Old Times
- Note: This table only includes levels that have been improved, as most of the levels use marzojr's inputs, and therefore remain unchanged.
| Stage & Act | New Time | Old Time | Improvement |
|---|---|---|---|
| Collision Chaos 1 | 0'15"43 | 0'15"66 | 0'00"23 Improvement |
| Collision Chaos 2 | 0'16"98 | 0'19"75 | 0'02"77 Improvement |
| Tidal Tempest 2 | 0'18"88 | 0'29"60 | 0'10"88 Improvement |
| Quartz Quadrant 1 | 0'15"53 | 0'15"88 | 0'00"35 Improvement |
| Metallic Madness 3 | 1'07"13 | 1'07"30 | 0'00"27 Improvement |
Total Time Saved: 0'14"50
Final Time: 8'54"55
Other Comments
Huge thank you to the following people:
- Zaxon96 for discovering the Collision Chaos 2 level wrap!
- CubbyCat for discovering the Tidal Tempest 2 level wrap!
- Werster for finding the QQ1 wrap!
- Xandre69 for posting tutorials on these tricks and overall being a great help!
- rodonic01 for creating a temporary encode for this run!
- marzojr for his Sonic CD TAS that made this possible!
I believe this run can be improved in a few places. In CC1, we need good subpixels to get the fast zip, AND also get the jump that marzojr used in his previous run to reach the zipping point faster than normal. And in TT2, you can zip and clip into the leftmost wall, but you cannot wrap through it due to the water level being too high. If you can get enough speed and good subpixels to clip through both walls without waiting for the water level, you can easily save a few seconds.
Technical Information
Emulator Used: Gens Re-Recording v11b
ROM Checksum
- SHA1: 9819234d09c004f4ebe3a03d751edcb3ad6140dc
BIOS Used
- Mega-CD (J) - Model 1 v1.00p (1991).bin
ThunderAxe31: Claiming for judging.
ThunderAxe31: Accepting as improvement over the current publication.
despoa: Processing...
feos: Restored rerecord count.