Sonic the Hedgehog

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Version differences

As with all the 16-bit Sonic games, the PAL version runs 17% slower than the NTSC version. However, the in-game timer is slowed down by the same amount, so identical times are possible in both versions. PAL players may have a slight advantage due to the slowdown aiding players' reactions, but in general players in all regions can compete equally.

Terminology

Frame

1/60th of a second, the smallest unit of game time.

Frame window

the amount of these units you have to execute a particular action. A "frame-perfect" action has a window of just one frame, for instance.

Universal timer

There's two different timing properties of moving objects in this game. The universal timer is where an object starts moving the instant you start the level, and will therefore be in a certain position at a certain time, every time.

Camera timer

The other kind is this one, which only starts moving once it's brought onto the screen (or near the screen - when the object is first rendered, in any case). Knowing which objects have which timing properties is important to good times when you have to deal with them.

Ramp jump

Sonic's jump speed and height are dependent on both your speed going into the jump and the slope of the ground you jump off. Running up a slope causes your jump to become much higher, while running down a slope will make you jump quite flat to the ground, gaining speed. This applies even if the slope is very small.

Loop jump

Similar concept, but inside a loop. If you're moving through the loop from left to right, a loop jump is from the top-left to the bottom-left. It's kinda finicky because if you land at different angles you get different speeds, but in the best case it is faster, and it's also a very convenient way to switch from rolling to running.

Path switcher

This is an invisible item in the game that allows the levels to work as structured. There are three different levels of background/foreground and Sonic is always in one of them at any one time, and these items seamlessly switch Sonic from background to foreground and vice versa. This is especially necessary for things like loops to work, because if you didn't have them they would just be solid all the time and you wouldn't be able to enter it. Knowing where these are and how they work is key to some tricks in this game.

Speed cap

Oddly for a game designed and marketed around speed, there are certain situations where the game will actually limit your speed. If you hold the direction you're moving and you're above the speed cap, the game will knock your speed back to the speed cap. This can be circumvented just by not pressing right.

Zip

A zip occurs when Sonic is stuck in a wall somehow and presses left or right. Since collision detection is designed to stop you from going into a wall in the first place, pushing left against a wall makes the game push you back to the right so you aren't embedded in it. As a result, when you're already inside a wall holding left or right causes you to travel in the opposite direction much faster than you can attain by normal play.

Level wrap

This is what happens when a zip causes you to bypass the left edge of the screen. The game treats your X-coordinate in memory as a number less than 0 - but position coordinates are unsigned, so instead of a negative number it's a VERY large positive one - which correlates to the end of the stage.

More detailed information

TASvideos has a much more in-depth analysis, mostly dealing with the way the engine works. It can be found at http://tasvideos.org/GameResources/Genesis/SonicTheHedgehog.html (this covers all three games in the classic series).

In-game Time vs. Real Time

In all of the classic Sonic games, completing levels very quickly (in Sonic 1, under 30 seconds) gives a 50,000 point time bonus. Completing a level between 30 and 45 seconds gives a 10,000 time bonus instead. On the act clear screen, the bonus ticks down at a rate of 100 points per frame, and cannot be skipped. What this means is, in real time it would in fact be faster to wait for the timer to tick over to 30, as long as the time you would otherwise get is between 23 seconds, 20 frames (0:23::20) and 30 seconds even. The Sonic playing community generally agrees that this is pretty dumb, and the time spent actually playing the stages is what matters, so these games are timed by taking the sum of the in-game times for each level.

For a further explanation, this video does a good job of explaining why in-game time matters in certain games, particularly in the Sonic franchise.

Best Times

The current best known times for Sonic 1 ILs are on The Sonic Center: http://soniccenter.org/rankings/sonic_1/times