Front Line is an arcade game produced and released by Taito in 1982. In it, a lone soldier clad in periwinkle fatigues and a red Brodie helmet, armed only with a revolver and a satchel of grenades, must advance through an onslaught of soldiers and tanks to destroy the enemy fortress. The perspective is top-down, and the screen scrolls vertically (and horizontally somewhat) as the hero progresses through the game. While it is not Taito's most polished game, Front Line was quite innovative and rather popular. Taito's competitors took notice as well, shortly releasing games utilizing similar themes and design elements, such as Commando and Ikari Warriors. Influenced by the foundation laid by Front Line, this style of game would propagate at arcades for years to come. The control scheme is innovative as well, pairing a joystick for moving the hero, a button to throw grenades or enter and exit a tank, and a combination spinner/button that could be rotated to change the hero's aim, and also pressed like a button to fire the gun.

Blitzkrieg:

Ordinarily, the Hero travels at a rate of 3 pixels per each 4 Frames, or .75 pixels per Frame. Using this technique, the Hero can travel at a rate 42 times greater: 126 pixels per each 4 Frames, or 31.5 pixels per Frame. This is effectively half a screen of travel for each increment of Hero movement. Hold Up and Down on the joystick simultaneously to cause the Hero to rush forward. Holding Left on the joystick in addition to holding Up and Down reduces the Hero's vertical speed to 33% of his maximum to 42 pixels per each 4 Frames (10.5 pixels per Frame), and also causes him to walk to the right at the normal rate of 3 pixels per each 4 Frames. This is useful in a situation where travelling at maximum speed would cause the Hero to overshoot his destination, but traveling at normal speed would be too slow. Note that holding Left on the joystick in addition to holding Up and Down prior to about the end of Screen Y High 8 allows a Hero Tank to spawn, which prevents Blitzkrieg for 20 Frames. As a point of reference, even if the Hero could advance to the Fort without interruption at his normal rate (which he can not), it would require 47,600 additional Frames...nearly 3 times as long as the entire TAS.

RNG Manipulation:

Everything the Hero does affects the RNG. The RNG determines the Map Configuration to be used, and the spawn location of Mines, Soldiers, and Tanks. The RNG is manipulated throughout the TAS in order to ensure optimum efficiency and maximum points.

Completion Requirement:

This TAS completes 10 Stages. Beyond Stage 10, all point values remain the same, and the Bonus Point at the end of a Stage remains 10,000 points.

There are 7 different possible Map Configurations. Each Map Configuration has obstacles at different locations. The specific Map Configuration used is determined by the RNG. On Map Configuration 4, the configuration of obstacles makes it impossible to use uninterrupted Blitzkrieg through the Stage.

Certain circumstances can cause the Fort Soldier to move at about 66% of his normal speed as he is thrown from the Fort explosion. Because the transition can not continue until the Fort Soldier has despawned, this would require an additional 34 Frames. This condition is set at the start of a Stage and can not be changed during the Stage. Instead, the RNG is manipulated during the previous Stage in order to prevent this condition.

Input can only be entered every 4th Frame.

If another enemy occupies the Fort's memory location, the Fort will fail to spawn when its spawn location is scrolled onto the screen.

If an enemy occupies the Fort's spawn location when the Fort is scrolled onto the screen, the enemy is despawned.

A Fort may be destroyed as many as 8 Frames earlier or later, depending on the Frame on which the Hero advances after throwing a Grenade.

The playfield extends from X 184 on the left and X 56 on the right, a width of 128 pixels. The center of the playfield is X 120.

Gun can be fired once per each 8 Frames, provided there are not 2 projectiles on the screen.

When a Fort is hit with a Grenade, the controls are immediately locked, and enemy activity is stopped. However, any projectiles that had been fired prior to the Fort being hit remain active. If a projectile hits the Hero, or if the surrendering Soldier contacts the Hero as he moves down to the Fort, the Hero will be killed, and the transition to the next Stage is interrupted.

During the transition to the next Stage, if the Tank's projectile collides with an object, it will be destroyed.

During the transition to the next Stage, if the Tank collides with an object, the game will freeze.

When the Hero reaches Screen Y High 14 Screen Y Low 192, the screen is automatically scrolled an additional 15 pixels to Screen Y Low 207. This is presumably to allow the Fort to fully render and attack, rather than being made vulnerable through precise scrolling.

As with a Fort, when a Hero Tank is partially scrolled onto the screen, the screen is automatically scrolled an additional 15 pixels. Note that during the 20 Frames of automatic scrolling, Blitzkrieg can not be used, and the Hero travels at the normal rate of 3 pixels per each 4 Frames.

The nearer the Fort is to the top of the screen when it is destroyed, the shorter the distance the surrendering Soldier has to move in order for the transition to the next Stage to begin.

When a Grenade is thrown straight ahead, its path curves to the right considerably (to simulate an arc) before landing at its original X location. Due to the shape of the Grenade's path, a Grenade thrown from the left of a target will hit the target on an earlier Frame than a Grenade thrown from the right of a target.

If the Fire button and the Grenade/Tank button are pressed simultaneously, the Grenade/Tank button takes priority, and the Fire button will fail. Joystick input can be used simultaneously with any other input.

Maximum Bonus Point is 10,000.

The Hero can be killed while he is jumping into a Tank.

A Boulder will also destroy a Soldier or Mine.

Enemy Soldiers are so lethally accurate, they can still fire and hit the Hero while he is travelling at 31.5 pixels per Frame.

The Hero is allowed to have a maximum of 2 projectiles on the screen at any given time. These projectiles can be 2 Bullets or 1 Bullet and 1 Grenade, but not 2 Grenades. A Bullet can not be fired on the Frame before another projectile spawns or despawns. Note that a projectile is still in memory until its impact sprite or explosion has expired.

Surrendering Soldier moves at a rate of 2 pixels per each 4 Frames.

The minimum distance that Surrendering Soldier must travel is 40 pixels, From Y 248 to Y 208. The screen must be scrolled no farther than Screen Y Low 222; otherwise Surrendering Soldier will have to travel farther down than Y 208.

Fort is located at Screen Y High 15.

When the Hero reaches Screen Y High 14 Screen Y Low 192, the screen is automatically scrolled an additional 15 pixels to Y 207. This is presumably to allow the Fort to fully render and attack, rather than being made vulnerable through precise scrolling.

After the Hero has reached Screen Y High 14 Screen Y Low 138, moving at maximum speed for 1 more increment would cause him to overshoot the Fort and move to Screen Y High 15 Screen Y Low 8, which would make Fort inaccessible. Instead, Left is held on the joystick in addition to Up and Down. This reduces the Hero's speed to 33% of his maximum to a more manageable 42 pixels per each 4 Frames, which allows him to continue to rush forward a bit farther before needing to resort to normal walking.

The center of the playfield is X 120.

Hero must be between X 105 and X 144 and at Screen Y Low 186 or nearer in order to throw a Grenade straight ahead from maximum range and hit the Fort.

Hero must be at X 102 or farther right in order to avoid being hit by a Fort projectile fired straight ahead.

Hero must be at X 135 or farther left in order to avoid being hit by a Fort projectile fired straight ahead.

The Point value for destroying an enemy is multiplied by the Stage number, to a maximum multiplier of 10 on Stage 10 and beyond.

Destroying Soldier is worth 100-1000 points.

Destroying Tank with Tank is worth 100-1000 points. Tank can only be destroyed with Grenade or another Tank.

Destroying Tank with Grenade is worth 200-2000 points. Tank can only be destroyed with Grenade or another Tank.

Destroying Fort is worth 200-2000 points. Fort can only be destroyed with Grenade.

Destroying Mine scores no points.

Each Stage is fundamentally the same, in that the Hero must rush to Screen Y High 15 and destroy the Fort with a Grenade.

For optimum efficiency on a Stage, the following criteria must be met:

1.) Map Configuration must not be Map Configuration Type 4, or else Blitzkrieg will be interrupted.

2.) Soldier spawn locations must be safely navigable without delay in Segment 1. For the purposes of this TAS, all Soldiers must spawn such that they can be destroyed for maximum score.

3.) The Fort's memory location must not be occupied when the Hero arrives at the Fort's spawn location, or else the Fort will fail to spawn.

4.) Tank spawn locations must be safely navigable without delay on the final approach to the Fort.

5.) Tank spawn locations must not impede Grenade.

6.) The screen must be scrolled no farther than Screen Y Low 222; otherwise Surrendering Soldier will have to travel farther than the minimum of 40 pixels before the transition to the next Stage can continue.

7.) The Fort must be destroyed on the earliest possible Frame.

8.) Input for the current Stage must not cause the subsequent Stage to fail to meet any of these criteria.

Precise control and RNG manipulation are used throughout the TAS to ensure that these 8 criteria are met on each Stage. Note that for Stage 10, only criteria 1-5 are strictly necessary, as the priority changes to ending input as early as possible. For Stage 10, the Grenade is thrown on a later Frame, but such that using the automatic screen scroll to the Fort allows input to be ended immediately after throwing the Grenade, rather than needing to walk forward after throwing it.

feos: This is an ever-looping game, and it has seemingly increasing difficulty, but the glitch used here renders the difficulty changes barely relevant. Going along with the author's choice here. Reviews are mixed, people seem to feel like it would have looked better without the glitch, but I'm pretty sure it'd only go to Vault either way. Accepting.

TheCoreyBurton: Processing.