Nemesis (Arcade)

To do: Document the US prototype version included in Gradius Origins (currently undumped in MAME).

Nemesis is Konami's 1985 arcade game that's better known by pretty much everyone at this point as Gradius, its original Japanese name. Your precious Konami Code can't save you now!

Unused Graphics#

This square-shaped robot has what looks like a diamond-shaped pinball flipper. Seems like it could shoot out bullets, maybe? Sounds about right.

Another unused enemy design that kind of looks like a pinball bumper.

Unused Music#

Regional Differences#

• bs_gradius is the original Japanese version. It runs on the Konami Bubble System hardware. This is known internally as Version A.
• gradius is the Japanese version converted from the Bubble System to a standard on-board ROM (exactly the Konami Nemesis/GX400 Hardware) due to the commercial failure of the Bubble System for being more expensive than ROM boards and extremely sensitive to electromagnetic fields. Despite being a hardware conversion, waiting times have only been reduced and like gradiusb this is known internally as Version A.
• nemesisuk is the European version of the game and assumed (by MAME, anyway) as "World". Unlike gradius, the game is not a conversion of the original Bubble System version, but a version of the game rebuilt from scratch directly on the Konami Nemesis/GX400 hardware. Because of this, waiting times are removed and the Morning Music sequence was removed and replaced with a standard RAM/ROM check. This version plays like gradiusb/gradius, but it has some gameplay and aesthetic changes, later reused in nemesis. This is known internally as Version E.
• nemesis is the North American version of the game. Based entirely on nemesisuk, this version has a number of coding changes, some of which it shares with nemesisuk and a harder overall difficulty. This is known internally as Version D.

Test Mode Changes#

Gradius	Nemesis

Text in the test mode screens uses palette 0A in Gradius and palette 00 in Nemesis. It's not clear if this is a bug or some kind of attempt to make the text more readable. If it's the latter, they missed the Demo Sound and Coin A / B dip switch variables.

nemesis	nemesisuk

In the nemesisuk set, the text "EVERY BONUS", used for subsequent bonus lives, was rewritten to the more accurate "AND THEN EVERY".

Game's Startup#

Each set features a different game's startup:

• bs_gradius features the famous Konami Morning Music routine where the game greets you with a screen saying "WARMING UP NOW PRESENTED BY KONAMI" and a warm-up countdown of 100 seconds. During this time, "Morning Music" will play as the countdown goes down, giving you a nice melody to listen to as the game readies itself up. Once the sequence ends, you'll be greeted with the title screen, and the game logo appears slowly drawn onto the screen.
• gradius features the same Morning Music routine from the original set, but due to the conversion from the Bubble System to the Nemesis/GX400 hardware, the warm-up countdown sequence is shortened (from 1 minute and 30 seconds to just 25 seconds), noticeable by the warm-up countdown which goes down faster than it used to on the Bubble System hardware. Unfortunately, this also means that the "Morning Music" can no longer play in its entirety. Once the sequence ends, you'll be greeted with the title screen, and the game logo appears drawn onto the screen much faster than gradiusb.
• nemesisuk and nemesis, due to being versions created for the Nemesis/GX400 hardware from scratch, completely replace the Morning Music routine with a standard RAM/ROM check. The check starts with the screen being flooded full of garbage graphics, then it'll perform the RAM/ROM check. Once it ends, you'll be greeted with the much-cooler looking title screen based on the game's arcade flyer. After a few seconds, the background becomes a bit darker and the game's logo along with the standard text appear on the screen. Here, the game's logo appears without any effects, unlike gradiusb and gradius.

Title Screen#

Gradius	Nemesis

In addition to the obvious title change from Gradius to Nemesis, the title screen in the overseas version features a background as opposed to a black void, based on the artwork seen on the game's arcade flyer.

Game Demo#

Starting Lives#

Players start with 3/4/5/7 lives in bs_gradius, gradius and nemesis, depending on the how the "Lives" dip switches are set. In nemesisuk, this was changed to 2/3/5/7 lives.

Respawn Delay#

After losing a life, you have to wait a little before resume playing in gradiusb and gradius:

• In bs_gradius the respawn delay lasts from a minimum of 3 seconds to a maximum of 5 seconds.
• In gradius the respawn delay lasts from a minimum of 1 second to a maximum of 1,5 seconds.

In nemesisuk and nemesis there's no respawn delay, so you respawn instantly.

Continue#

The US nemesis set is the only version that allows you to continue after losing your last life. In bs_gradius, gradius and nemesisuk, losing your last life means game over and restart the game back from the beginning. nemesis allows you to continue only up to three times, so losing your last life for the fourth time will result in the same gradiusb, gradius and nemesisuk outcome.

Note that in nemesisuk, the text for the continue screen is still in the ROM, but unused.

Support Name#

Gradius	Nemesis

The orange orbs that follow and fire with the ship are called Options in Gradius and Multiples in Nemesis.

Game Flow Changes#

Changes that make the boss fight portion of each stage take less time.

• The volcanic eruption at the end of stage 1 lasts 1024 frames in Gradius, but just 512 frames in Nemesis.

In Gradius, the volcanoes will first erupt slowly, then speed up every 128 frames. Max speed is reached at 512 frames.

In Nemesis, they will erupt just once at the slowest speed before suddenly switching to the fastest speed.

• The enemy rushes in stages 3 and 4 last 1004 frames in Gradius and 768 frames in Nemesis.
• At the end of stage 5, it takes 1016 frames for the boss to show up in Gradius. This wait was completely removed from Nemesis.
• At the end of stage 6, the boss barrier will self-destruct after 260 frames in Gradius. This is just 10 frames in Nemesis.
• The final boss self-destructs in 688 frames in Gradius and 656 frames in Nemesis.

Difficulty Changes#

The actual game difficulty is calculated through the following formula: (TimerVar + LevelNum + BonusVar + OptionsNum + DipVar) / 2. This value is capped at 15.

• TimerVar is the amount of time elapsed since the last death. In the original sets, this increments every 1000 frames. In nemesis, it will increment every 768/608/512/384 frames, depending on the value of the difficulty dip switches.
• LevelNum is how many levels you have completed. In the original sets, this value is multiplied by 3 for calculation's sake, while nemesis just uses the raw value.
• BonusVar adds difficulty based on the power-ups you collected. Like the TimerVar, these values are static in the original sets and vary with the difficulty dip switches in nemesis:

:* If you have the Missile upgrade, add 2 in the original sets and 1/2/2/3 in nemesis.

:* If you have four Options, add 2 in the original sets and 1/2/2/3 in nemesis.

:* If you have the Laser upgrade, add 4 in the original sets and 3/3/3/4 in nemesis.

:* If you have the Shield upgrade, add 4 in the original sets and 4/7/8/10 in nemesis.

• OptionsNum is the number of Option ships you have, multiplied by 2 in the original sets and by 2/3/4/5 in nemesis.
• DipVar is the numerical value of the difficulty dip switches.

:* In the original sets, Easy is 0, Normal is 2, Hard is 4, and Very Hard is 6.

:* In the nemesis set, Easy is 0, Normal is 4, Hard is 8, and Very Hard is 10.

Both TimerVar, BonusVar, and OptionsNum are set to 0 at the start of each game loop.

Fan bullet speeds
Note that there are four different Fan subtypes: One that never attacks, one that only attacks if the difficulty is greater than 7, one that only attacks if it's greater than 11, and one that always attacks. They all use the same bullet speed table, they just have different jumping-on points.

	Difficulty Value
	0
Original	1.000
Altered	1.000

Dee-01 bullet speeds and firing delay
If difficulty > 7, Dee-01 will fire 2 shots in a row; If difficulty > 11, Dee-01 will fire 3 shots. The delays listed here apply after the last shot is fired.

	Difficulty Value
	0
Original	1.125 112 frames
Altered	1.125 104 frames

Jumper bullet-spread counts

	Difficulty Value
	0
Original	3
Altered	3

Hatch-type enemy spawn counts

	Difficulty Value
	0
Original	3
Altered	3

Beans bullet speeds

	Difficulty Value
	0
Original	1.125
Altered	1.125

Mother fire delays & spawn counts

	Difficulty Value
	0
Original	64 frames 2x Child
Altered	64 frames 4x Child

Laser cannon / Big Core laser speeds (Measured in pixels per frame)

	Difficulty Value
	0
Original	2.00
Altered	2.00

Bonus Life Settings
The score thresholds for extra lives are higher in nemesis:

Enemy Layout Changes
There are a few changes in enemy placement in Stages 1 to 3.

Original	Altered

At the start of the main area of Stage 1, there's an extra Uros enemy on the ceiling.

Original	Altered

Three extra Ducker enemies are on the ceiling in the middle of Stage 1.

Original	Altered

The last enemy section before the large rock wall in Stage 2 has nine green and seven red Dee-01 enemies in the original game. nemesis removes two of the red Dee-01s, meaning there's less opportunity for power-ups, adds three more green Dee-01s, and places more of them at the bottom of the area.

Original	Altered

The very start of Stage 3 is much more populated in nemesis, with three orange and four normal Garun ships. Three of the four Garun enemies on the right were removed, and the remaining one was repositioned.

Original	Altered

Two more Mother enemies were added to this area in nemesis, bringing the grand total up to three. The last three Garuns were deleted.

Orange Enemies's Fleet

Original	Altered

After losing a life in nemesis, the game spawns a fleet of orange enemies to help you power up more easily. No such feature is present in the original versions.

References#