[[File:Viper_Phase_1_Logo_Dark.png|400px|center]]

{{GameInfobox
|bordercolor = black
|title = Viper Phase 1
|background = #f8f8f8
|image = Viper_Phase_1_Title.png
|width = 324px;
|imagecaption = Title screen
|imagescalepx = 180px

|developer = [[Seibu Kaihatsu]]
|
|music = Go Sato
|
|program = Yoritaka Kasai
|
|art = Toshinobu Komazawa
|
|releasedate = May 1995 (Japan)

|previousgame = [[Raiden DX]]
|nextgame = [[Raiden Fighters]]
}}

'''Viper Phase 1''' (バイパーフェイズ1) is a 1995 vertically scrolling shooter video game developed by Seibu Kaihatsu for arcades. Often regarded as a spin-off or spiritual successor to the Raiden series, the game shares many similarities in terms of gameplay mechanics and design philosophy. Viper Phase 1 is the first game developed for Seibu Kaihatsu's SPI system board, featuring detailed sprite-based graphics and elaborate explosion effects.

The initial release (now known as ''Old Version'') failed to gain acceptance among many players due to its unorthodox weapons system. Three months later, a revised '''New Version''' was released, featuring adjustments that brought the gameplay closer to Raiden, such as making sub-weapons permanent. This version also formed the basis for overseas releases of Viper Phase 1.

Hamster Corporation released the game as part of their Arcade Archives series for the Nintendo Switch and Sony PlayStation 4 in December 2024.

{{VideoIndex}}
__TOC__
{{clear}}

== Gameplay Overview ==
The game consists of eight stages and supports two-player simultaneous play. There are no extends.

=== Controls ===
----
* '''8-way joystick:''' Moves the player's craft. As in the Raiden series, diagonal movement is faster than strictly vertical or horizontal movement (with vertical movement being slower than horizontal movement).
* '''A:''' Simultaneously fires the player's main weapon and sub-weapon.
* '''B:''' Activates the player's bomb. There is a slight delay before the bomb detonates.

=== Weapons ===
----
Sub-weapons can be equipped by destroying a weapon carrier craft and picking up the weapon change item it drops. Weapon carriers generally appear in sync with specific enemy ships during the stages and can also appear during boss battles. Weapon change items float down the screen oscillating right and left and changing their weapon type every time they change direction. The starting weapon type is random, but the cycle order is fixed as Wide, Laser, Missile, Napalm, Wide, Laser... and so on.

{| class="wikitable"
|-
! scope="col" style="width: 80px;" | Icon
! scope="col" style="width: 80px;" | Name
! scope="col" style="width: 330px;" | Function
|-
| [[File:Viper_Phase_1_Wide.png|50px|center]] || <center>'''Wide'''</center> || <center>Fires shots in a fan-shaped pattern covering a wide area. Powering up expands the firing range. While the damage per individual shot is low, point-blanking enemies unleashes devastating attack power.</center>
|-
| [[File:Viper_Phase_1_Laser.png|50px|center]] || <center>'''Laser'''</center> || <center>Fires a laser beam straight ahead. Although the effective range is narrow, the weapon is powerful. Powering up increases the thickness of the beam. This weapon is effective against heavily armored enemies.</center>
|-
| [[File:Viper_Phase_1_Missile.png|50px|center]] || <center>'''Missile'''</center> || <center>Launches missiles across a wide area in front of your ship. The missiles travel slowly but explode upon impact, dealing massive damage. Powering up increases the number of missiles fired and expands the size of the resulting explosions.</center>
|-
| [[File:Viper_Phase_1_Napalm.png|50px|center]] || <center>'''Napalm'''</center> || <center>Fires missiles straight ahead from both wings of your ship. They detonate upon impact, dealing concentrated, high-damage hits. Powering up increases the number of explosions generated by each missile, allowing the blast to cover a wider area.</center>
|-
|}

=== Items ===
----
Destroying item carriers that appear at predetermined points throughout each stage will release either a power-up item or a bomb item. These items appear in a repeating power-up, power-up, bomb, power-up, power-up, bomb... sequence with every item carrier destroyed.

Medals can be revealed by destroying various airborne and ground-based targets.

{| class="wikitable"
|-
! scope="col" style="width: 80px;" | Icon
! scope="col" style="width: 80px;" | Name
! scope="col" style="width: 330px;" | Function
|-
| [[File:Viper_Phase_1_Powerup.png|50px|center]] || <center>'''Power-up'''</center> || <center>Upgrades both the main weapon and sub-weapon shot power up to a maximum of three levels. However, if you choose the Laser or Napalm sub-weapon, your main shot is downgraded to its weakest form.<br>

In Old Version only the main weapon is upgraded.</center>
|-
| [[File:Viper_Phase_1_Bomb.png|50px|center]] || <center>'''Bomb'''</center> || <center>Increases the player bomb stock by 1.</center>
|-
| [[File:Viper_Phase_1_Medal_Small.png|50px|center]] || <center>'''Small medal'''</center> || <center>Worth 500 points, or 2,000 points at max value.</center>
|-
| [[File:Viper_Phase_1_Medal_Large.png|50px|center]] || <center>'''Large medal'''</center> || <center>Worth 1,000 points, or 3,000 points at max value.</center>
|-
| [[File:Viper_Phase_1_Medal_Special.png|50px|center]] || <center>'''Special medal'''</center> || <center>Worth 30,000 points, or 100,000 points at max value. Can be revealed twice in the game.</center>
|-
|}

=== Rank ===
----
In Viper Phase 1 rank is chiefly a survival timer. As you stay alive, rank gradually climbs toward its maximum. Dying lowers rank—normally by 2 levels in single-player on default settings and delays the next increase. The rate is determined by the current stage and DIP difficulty.

Higher rank:

* allows more enemy bullets on screen;
* changes when enemies are permitted to shoot;
* shortens enemy timers;
* increases enemy bullet speed;
* activates harder behavior in numerous enemy-specific scripts.

Power level doesn't raise rank, but it adds a small amount to the separate bullet-speed difficulty calculation.

=== Loops ===
----
If a game features a [[loop]] system, elaborate on it in detail here. ''Otherwise, omit this section.''

=== Endings ===
----
There are two narrative outcomes determined by whether you stop the planet-destroying missile in Stage 8. Depending on the ending reached a different completion bonus is awarded.

=== Scoring ===
----
This section refers primarily to the New Version of the game.

=== Ground Medals ===

At regular intervals ground medals will have a brief moment where they stop shimmering. Collecting them at that exact moment awards the maximum value of 2,000 points or 3,000 points, respectively, for small and large medals, as well as 100,000 points for a special medal.

=== Airborne Medals ===

Airborne medals do not feature a shimmering animation and will always be worth the base value of 500 points or 1,000 points, respectively, for small and large medals.

In most cases, airborne medals will be released by specific medal carrier enemies. These enemies appear at a random horizontal position and at fixed times for each stage based on the elapsed time from the start of the stage. They will descend straight down from the top of the screen, briefly pause when they reach their inflection point near the center, and then change their trajectory back up and off the screen. Destroying a medal carrier on the way down yields five medals, but destroying it only after it has begun to travel back up the screen will make it drop ten medals.

=== Stage Clear Bonus ===

At the end of each stage, the game awards a bonus based on enemies destroyed, medals collected, bombs remaining, and the destruction rate:

{| class="wikitable"
|-
| stage clear bonus = (enemies destroyed × 10 + bombs × 300 + medals × 100) × destruction-rate multiplier
|}

The destruction multiplier is determined by the percentage of enemies destroyed. For '''single-player''', the destruction-rate multiplier is as follows in the New Version:

{| class="wikitable"
|-
! scope="col" style="width: 100px;" | Percent Destroyed
! scope="col" style="width: 100px;" | Multiplier
|-
| <center>'''0–79%'''</center> || <center>x10</center>
|-
| <center>'''80–89%'''</center> || <center>x20</center>
|-
| <center>'''90–94%'''</center> || <center>x30</center>
|-
| <center>'''95–98%'''</center> || <center>x40</center>
|-
| <center>'''99%'''</center> || <center>x50</center>
|-
| <center>'''100%'''</center> || <center>x100</center>
|-
|}

There is no rounding to the nearest integer. So if the actual ratio is 98.99%, the game treats that as 98% → ×40, not 99% → ×50.

This makes a 100% destruction rate particularly valuable: the multiplier jumps from ×50 at 99% to ×100 at 100%, effectively doubling the entire stage clear bonus.

==== Two-Player Exception ====

In simultaneous two-player play, the multiplier table is slightly different:

{| class="wikitable"
|-
! scope="col" style="width: 100px;" | Percent Destroyed
! scope="col" style="width: 100px;" | Multiplier
|-
| <center>'''0–79%'''</center> || <center>x10</center>
|-
| <center>'''80–89%'''</center> || <center>x20</center>
|-
| <center>'''90–94%'''</center> || <center>x30</center>
|-
| <center>'''95–99%'''</center> || <center>x40</center>
|-
| <center>'''100%'''</center> || <center>x50</center>
|-
|}

==== Stage 4 Bug ====

Due to incorrect spawn coordinates, several enemies in Stage 4 are immediately deleted before the player can destroy them. As a result, a 100% destruction rate cannot legitimately be achieved in Stage 4; 99% is the maximum. The Old Version has an equivalent bug in Stage 6.

=== All Clear Bonus ===

After completing the game, an additional bonus is awarded based on final-mission success, total enemies destroyed, total medals collected, bombs used, and deaths.

{| class="wikitable"
|-
| all clear bonus = completion bonus + (total enemies × 100) + (total medals × 1,000) + bomb bonus + survival bonus
|}

==== Completion Bonus ====

If the missile in the final mission stopped, thereby achieving the good ending, 1,000,000 points are awarded. If the player fails to do so only 100,000 points are awarded.

==== Bomb Bonus ====

The Bomb Bonus is based on the total number of bombs used during the entire game:

{| class="wikitable"
|-
! scope="col" style="width: 100px;" | Bombs used
! scope="col" style="width: 100px;" | Bonus
|-
| <center>'''0'''</center> || <center>500,000</center>
|-
| <center>'''1'''</center> || <center>300,000</center>
|-
| <center>'''2'''</center> || <center>100,000</center>
|-
| <center>'''3'''</center> || <center>50,000</center>
|-
| <center>'''4'''</center> || <center>40,000</center>
|-
| <center>'''5'''</center> || <center>30,000</center>
|-
| <center>'''6'''</center> || <center>20,000</center>
|-
| <center>'''7'''</center> || <center>10,000</center>
|-
| <center>'''8'''</center> || <center>9,000</center>
|-
| <center>'''9'''</center> || <center>8,000</center>
|-
| <center>'''10'''</center> || <center>7,000</center>
|-
| <center>'''11'''</center> || <center>6,000</center>
|-
| <center>'''12'''</center> || <center>5,000</center>
|-
| <center>'''13'''</center> || <center>4,000</center>
|-
| <center>'''14'''</center> || <center>3,000</center>
|-
| <center>'''15+'''</center> || <center>2,000</center>
|-
|}

==== Survival Bonus ====

The Survival Bonus is based on the total number of deaths during the entire game:

{| class="wikitable"
|-
! scope="col" style="width: 100px;" | Deaths
! scope="col" style="width: 100px;" | Bonus
|-
| <center>'''0'''</center> || <center>500,000</center>
|-
| <center>'''1'''</center> || <center>400,000</center>
|-
| <center>'''2'''</center> || <center>300,000</center>
|-
|}

== Strategy ==

=== Basic Strategy ===

* Wide shot is the recommended sub-weapon for the entirety of the game due to its powerful point-blanking ability.

=== Enemy Spawn Behavior ===

Viper Phase 1 uses both fixed and dynamic enemy spawning. Fixed enemies are tied to specific stage scroll positions and therefore normally appear at the same place on every run.
Other, primarily airborne enemies belong to sequential wave lists whose timing depends partly on how quickly the previous wave is cleared. The game keeps a counter of active wave enemies; when it reaches zero, part of the delay before the next wave is skipped. If enemies survive, the next wave eventually appears anyway after a timeout. The order of these waves is fixed rather than random, so destroying enemies quickly changes their timing but not which enemies are scheduled to appear.

Players can manipulate the dynamic enemy spawning to suit their goals. Survival players may choose not to destroy certain enemy waves in order to prevent more difficult enemy combinations from appearing (for example in Stages 4 and 7), whereas score players may choose to speed kill successive waves in order to optimize the enemies destroyed bonus.

----
=== Special Medals ===
* This section would contain particularly advanced gameplay techniques and more scoring information.
* Ideally, this is information that you probably wouldn't tell someone who just picked up the game. Players looking at this section are typically aiming to reach the next level of play.

== Story ==
The year is 2050 (Cosmic Era), long after humanity embarked on a massive space colonization project in search of a "second Earth." Having settled across various star systems, humanity developed unique cultures and scientific advancements, yet simultaneously fell into conflict, sparking a succession of large-scale interstellar wars. The flames of war eventually reached Earth itself; a rebel force from another star system—possessing technology far superior to Earth's—brought a massive fleet led by a space aircraft carrier into Earth's orbit and demanded unconditional surrender. In response, the Earth Defense Force launched a top-secret operation codenamed "Viper Phase 1," the plan for which was to infiltrate the enemy carrier, gather data, seize a new type of enemy fighter, and then use that fighter to destroy the carrier.
----

== Development History ==
Viper Phase 1 was programmed almost single-handedly by Yoritaka Kasai, who handled the game's entire codebase — including system architecture, enemy behaviors, and boss encounters — while heavily struggling against the hardware limitations of the arcade board. To ensure broad appeal, simple controls and straightforward mechanics were maintained, though Kasai later made a business trip overseas to adjust the game's balance specifically for Western audiences, eventually introducing a medal-collecting mechanic in the New Version to cater to American player preferences.

Despite the tight schedule preventing full optimization during development, the foundational programming and system lessons from Viper Phase 1 directly paved the way for Seibu Kaihatsu's hit Raiden Fighters series.
----

== Version Differences ==
Viper Phase 1 exists in an original Old Version and a revised New Version. The American release, titled Viper Phase 1 U.S.A., is based on the New Version but also has some region-dependent differences.

=== Japan Old Version vs. Japan New Version ===

{| class="wikitable"
|-
! scope="col" style="width: 200px;" | Feature
! scope="col" style="width: 200px;" | Old Version
! scope="col" style="width: 200px;" | New Version
|-
| <center>'''Secondary weapons'''</center> || <center>Limited ammunition</center> || <center>Unlimited ammunition</center>
|-
| <center>'''Secondary weapon power'''</center> || <center>Fixed</center> || <center>Four power levels</center>
|-
| <center>'''Secondary weapon damage'''</center> || <center>Higher</center> || <center>Reduced</center>
|-
| <center>'''Power-up items'''</center> || <center>Power up the main shot</center> || <center>Also power up secondary weapons</center>
|-
| <center>'''Bomb activation'''</center> || <center>Slower</center> || <center>Faster</center>
|-
| <center>'''Medal system'''</center> || <center>Simple</center> || <center>Expanded timing-based scoring</center>
|-
| <center>'''Medal carriers'''</center> || <center>Less frequent</center> || <center>More frequent</center>
|-
|}

=== Japan New Version vs. USA New Version ===

Viper Phase USA uses essentially the same revised gameplay as the Japanese New Version. By default it is configured with a second loop after clearing the game.

The only confirmed regional gameplay adjustment is the enemy bullet-speed rank curve. The USA version is slightly more lenient at low rank.

----

== Trivia ==
* Cool facts and random tidbits go here!
----

== Gallery ==
<div style='text-align: center;'>
''See [[(Template Page)/Gallery]] for our collection of images and scans for the game.''
</div>
----

== Other ==

We have support for wikitables, giving us the potential to add lots of cool info in a small box on the page somewhere, but we are not using them at the moment. I'm just leaving this here so we can have it handy in case we decide to actually use them. Feel free to not use this section.

{| class="wikitable" style="float: right; margin-left: 10px;"
|-
! [[(Template Page)]]
|-
| put your stuff here
|}

== References & Contributors ==
<small>
# Remember to include everyone that you can in your credits if they contributed information! | Having links handy is even better, when available.
# If you are a primary source of information for a game, be sure to link to your Shmup Wiki user account by including a link to your profile, such as: <nowiki>[[User:(You)|(Your Name)]]</nowiki>
## And while you're at it, make yourself a little profile page (if you want, of course)! As a contributor, you deserve to be recognized for your efforts.

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