Game Mechanics

Misc. Explanations of Game Mechanics

Explanation by Heidman

Character Movement

Go right. Don't jump(if possible). When you jump you lose a frame of forward momentum. You also lose a frame of forward momentum when you land when you walk off an edge.

Spread Rhythm

Spread Rhythm in base stages Spread Rhythm in side scrolling stages With the spread gun, you can have up to ten shots on the screen at once (and 16 shots at once with two players). Press B twice and you'll usually end up with 10 shots on the screen - two waves of 5 shots. Let's say that three shots have left the screen before the other shots did. You've got have 7 shots on the screen so you're below the 10 limit. The game will let you fire another "wave" of spread, but it can't go above 10 so you get a "wave" of 3 spread shots. Let's say that you then had 8 shots on the screen, the next time you fire you get a "wave" of 2 shots and so on. The directions the shots go depend on how big the "wave" is, but it always has a shot going straight. The idea is that by rhythmic shooting you can get the "waves" of spread to shift into a straight stream. If you don't press the B button repeatedly at the right frequency the smaller waves will go offscreen and you'll get the broader waves of 5.

The process is the same for base stages, but it's much harder. Shots will usually disappear at the same time because they all hit the wall at the end of the hallway at the same time. If a shot hits an enemy or another object those enemy'the collision happens before the other shots hit the wall. You have 1/60th of a second to press the B button to get another wave off before the rest of the shots hit the wall. Keep repeating the process to get a straight stream of spread. If you don't press the B button repeatedly at the right frequency the smaller waves will go offscreen and you'll get the broader waves of 5.

Weapon Damage & Enemy Health

Stage 5 Snow Field Bomb Jump

Explanation video It's a one frame jump. Depending on how you approach the cliff the frame you need to jump shifts. With a bit of a feint you can avoid the jump and it will only cost you 12 frames.

Stage 6 Exo Strat

The Exo Strat
This is a video of the optimal way to get through the Energy Zone. You only have 15 frames of give throughout all the jumps.

Stages 6 & 7 Timings for Flames and Claws

Timing Explanation Video
Most of the flames and claws operate on a global timer. Some of them operate on a proximity timer.

Regional Differences

Runs done on the Japanese version of Contra can save a significant amount of time over runs done on the U.S. version. The Japanese version has a cut scene and a map scene which can both be skipped by pressing the start button. After skipping both stages, the next stage appears immediately. In the U.S. version, a mandatory transition screen that displays the stage number and score is shown before the next stage appears. There are 7 stage transitions with skippable cutscenes in the Japanese version. To convert the time, measure how much time was saved transitioning cutscenes in the Japanese version and subtract it from the amount of time spent watching mandatory stage transitions in the U.S. Version.

Converting time on the Japanese Version to the U.S. Version

 ((1497 - X)+ Y)

Where 1497 is the time in frames, X is the time it took you to transition between stages and Y is the time of your run. The TAS is able to advance between stages in 1.1 seconds so the stage transition time in real time can't be less than 1.1 seconds. A more friendly way of saying it is:

 ((24.95 seconds - Stage transition time) + Time of your run)

Note: You will need the RAW AVI file of your run on the Japanese version to do this.

• Start with 1497 frames (the time spent watching stage transitions in the U.S. version)
• Count the frames from when the screen turns black to when the next stage appears
  

You need to add these up for the following stage transitions:
Transition 1 - From Jungle to Base 1
Transition 2 - From Base 1 to Waterfall
Transition 3 - From Waterfall to Base 2
Transition 4 - From Base 2 to Snow Field
Transition 5 - From Snow Field to Energy Zone
Transition 6 - From Energy Zone to Hangar
Transition 7 - From Energy Zone to Alien's Lair

• Add the total number of frames together and subtract it from 1497

This method is currently accurate to within 5 frames. The formula may add an extra 5 frames to the Japanese Version time. Information on the testing method can be found on this spreadsheet

Other Differences

Gameplay Differences
In two player mode, the positioning of the sniper just before the first spread power up is slightly different
In two play mode, the positioning of the bombs in snow field are slightly different. Player 2 cannot run past all of the bombs in snow field, although player 1 still can.

Graphical Differences
In the jungle stage, the cliff looks slightly different
In the jungle stage, the leaves of the trees rustle slighty
In the waterfall stage, the cliff and water look slightly different
In the snow field, snow falls throughout certain sections of the stage
In alien's lair, the ground and ceiling pulsate

Glitches

Stage 3 Jump Glitch

Explanation of the jump glitch
This is how the glitch in stage 3 works where you can jump higher some times than other times. It's referenced on the TAS Videos resource page: http://tasvideos.org/GameResources/NES/Contra.html#JumpGlitch But this video goes into a bit more detail

Stage 4 Boss Quick Kill

Explanation of the boss Quick Kill
You basically hit the boss on the last frame that the heads are together to mess up the boss vulnerability flag when the head is split apart.