Celtreos



Celtreos is a 2D horizontal scrolling space-themed game created by Kevin Grant in 2017 (with continuous updates through 2023). It is available for macOS on Steam, and iOS and tvOS on the App Store. It supports one or two local players simultaneously.

Everything in the game is unlocked at the beginning; it is possible to start the game at any stage but all stages must be played in a sequence to see the game ending.

This game is notable for not only having power-ups but also power-down orbs (penalties), which temporarily inconvenience the player in various ways. These include: preventing scoring, reducing weapon power, reducing weapon range, slowing weapons down, preventing weapon switching altogether, or even eliminating weapons from your arsenal.

It is also possible to play this game on very large displays with good quality due to vector graphics.

Gameplay Overview
Celtreos supports one or two players simultaneously, with 7 playable ships and 13 stages. Each stage ends with a boss fight, and the final stage has two very long boss fights.

There is a power-up system, a large number of weapons and defenses (including special abilities that consume charges), a variety of different playable ships, and the ability to slow down.

Soundtrack
The game has a massive 27-song soundtrack, almost 45 minutes of music. The main options screen allows any song to be played, and the same options are available in-game. It is also possible to adjust the volume or turn off the sound.

Celtreos has the ability to interface with the music player from the OS (any app on iOS, or iTunes/Music on macOS). If these apps are playing music instead, the game exposes an option to auto-next-song for key game events (new stages or boss fights), allowing players to craft their own favorite soundtracks to suit the gameplay.

Controls
Celtreos supports a variety of different inputs: keyboard, mouse or trackpad (may be combined with keyboard or used separately), game controllers (MFi, Xbox, DualShock or DualSense), and touch controls on iOS. There is no way to remap the key or button assignments.

The ship fires weapons continuously.

Keyboard
 * W/A/S/D: Move up/left/down/right
 * Q: Rotate between available weapons
 * B or Touch Bar: Use special ability
 * Caps Lock: Toggle default speed
 * R: Switch back to most-recently-used weapon
 * 1 or Touch Bar: Switch directly to default weapon
 * 2 or Touch Bar: Switch directly to multiway-class weapon (if any)
 * 3 or Touch Bar: Switch directly to sideways-class weapon (if any)
 * 4 or Touch Bar: Switch directly to locator-class weapon (if any)
 * 5 or Touch Bar: Switch directly to destroyer-class weapon (if any)
 * 6 or Touch Bar: Switch directly to movement-opposing-class weapon (if any)

Mouse
 * Move mouse: Move in any direction
 * Left button (Press) + ⌘: Dash straight toward location
 * Left button (Hold): Temporarily switch speed while button is held
 * Right button: Rotate between available weapons
 * Double-click: Use special ability
 * 3rd button: Use special ability

Game Controller
 * A-button or DualSense X-button (Hold): Temporarily switch speed while button is held
 * B-button or DualSense circle-button (Press): Use special ability
 * X-button or DualSense square-button (Press): Toggle default speed
 * Y-button or DualSense triangle-button (Press): Switch back to most-recently-used weapon
 * L1/R1: Rotate between available weapons

Touch Screen
 * Drag with finger on screen: Move in any direction
 * Tap elsewhere on screen: Dash straight toward location
 * Other abilities have onscreen controls

Unlockable Secrets
There are a number of “Achievements” that can be scored in the game, which make your player invincible for several seconds, including the ability to float through walls.

The conditions to discover each Achievement are secret but they range from almost unavoidable (like scoring a certain number of points) to somewhat difficult (there is one that requires you to obtain a certain number of special-ability charges, which can only be done if you go through much of the game without ever using special abilities).

There are currently at least 8 ways to score an Achievement.

Ships
There are 7 ships available. The differences are mostly cosmetic, except that larger ships will be harder to navigate safely in tight spots and weapons with more than one starting point (such as “Phaser”) will be anchored differently on each ship design.


 * Flyer of Fire, Mark II
 * Armaton
 * Mini
 * Elwing
 * Jade Piercer
 * Beryl Blade
 * Verdigris Viper

Weapons and Defenses
In Celtreos, abilities are gathered into weapon arrays and you can customize all of them in the options screen at the start of the game. In a given stage, you have just one default weapon and rely on power-ups to gather more (and you can lose them if you die, unless you set a preference in the game to prevent this or obtain a Preserver power-up).

At the end of every boss fight, one to three alternate weapon arrays spawn, giving you the opportunity to swap out your abilities if you want to.

The “Gun Mount” preference setting can be used to influence weapon firing patterns, especially when combined with multipliers (“×2” or “×3”).

Each weapon array has slots that categorize behavior, and (see “Controls” above) each type can be accessed directly from the keyboard as long as you have acquired the right power-up.

Note: There is a guide to Celtreos Weapons on Steam (see “References & Contributors” below).

There is a special ability in each array:
 * Bomb: Damage covering a large area on the screen
 * Lightning: Heavy damage in a cone behind the ship
 * Ray Burst: Rapid enemy-seeking lasers for several seconds
 * Time Warp: Not an attack but a way to slow down enemies on the screen for several seconds
 * Concentrator: Extensive damage covering a narrow area in front of the ship

In addition, each array has one type of protection:
 * Shield: Worn down when damaged
 * Deflector: Bounces attacks in new directions (an interesting defense in two-player games)
 * Armor: Regenerating plates that also have a melee attack
 * Barrier: A mixture of deflection and attack

The array also determines the type of defenders that can be acquired, up to 5 at once; these occupy different positions on the screen and aid your main ship:
 * Defender: Orbs that rotate around your ship, damaging anything they touch
 * Shadow: After-images that provide additional forward cover fire
 * Trailer: After-images that provide additional backward cover fire
 * Sentry: Flying drones that shoot lasers at nearby foes
 * Prism: Fields that can drastically alter weapon trajectory

Items
Items are both good and bad; they can spawn randomly, float in the game world, or show up after destroying small power-up ships. Weapon arrays will only spawn at the end of a stage, immediately after the boss fight ends.

If a power-up is obtained, the game speaks the name of the new weapon! (The volume of these vocals can be configured separately from other sound effects, as well.)

Good Items

Bad Items

Player Death
Most enemy attacks will kill the player instantly unless a defense is active (for example, “Shield” might absorb the entire attack and become weaker but the player is saved). The player’s ship is also destroyed immediately by hitting walls, as well as most boss ships, and defenses will not save the player from these collisions.

At time of death, all weapons and defenses are lost (unless the “Keep weapons after death” game setting is in effect, or a “Preserver” is in effect; see “Items”), and the main weapon’s power is reduced to minimum. The number of “charges” left for special abilities is not reset.

When the player dies, there is a chance that power-ups will spawn. These may include most of the weapons and other abilities that the player had, or a single very useful item (like “1UP” or “Rapid Fire”). It is also possible that nothing will happen.

The number of lives left is only displayed on the screen at time of death.

Lives can be configured from 1-9 at the beginning of the game. They can be gained in-game with the “1UP” power-up (see “Items”), and also every 250,000 points (see “Scoring”). In two-player games, each player has a separate Lives counter.

There are no “continues” in Celtreos; once all lives are lost the game is over. The “GAME OVER” display remains on screen until dismissed, and the current stage continues to scroll and enemies still appear (including the boss at the end). Thus, you can see a preview all the way to the end of an unfamiliar stage by waiting at the Game Over screen. Power-ups do not appear in Game Over mode so you will still not know where those would have spawned.

Observable Screen & Playing Field
Most stages are two “screens” high, where the player can move toward the top or bottom edges of the screen to gradually scroll and reveal a different area. In two-player games, both ships must be near the top or bottom to trigger scrolling.

Some stages will periodically rotate the entire play field, causing enemies and power-ups to come from unusual directions.

Scoring
Scoring is primarily useful for gaining new lives every 250,000 points, and Achievements (though many Achievements are not based on score).

Two of the power-ups in the game can boost score (by 500 points, 2500 points or 10000 points) and they are generally placed in optional areas that may be tricky to reach.

At the end of every stage there is a time bonus for finishing relatively quickly, and a shooting bonus for destroying lots of enemies.

Strategy
See Celtreos/Strategy for stage maps, enemy and boss descriptions, walkthroughs, and advanced play strategies.


 * Boss fights will be easier if you find vulnerable spots such as turrets and destroy those first, even if they do not count toward the boss’ total health. Also, do not waste time; some bosses will regenerate a shield after awhile!


 * At the end of every boss fight, one to three alternative weapon arrays will always spawn. You do not have to change out your weapons but once you become familiar with each stage you may find that certain abilities will work better than others in a given stage.


 * Learning the exact conditions for an Achievement, and then timing it, can be very helpful to make progress in the game. For example, if you are nearing a boss fight and close to a key score, holding off on shooting a few enemies may help you to time the Achievement during a difficult phase of the boss, and gain crucial seconds of invincibility!


 * Every stage has exactly 3 gold “Fragments” that are worthless unless you get all 3 of them. Learning where these can be is very useful because they will cause many useful power-ups to spawn (although the exact set is random).  In some stages a Fragment may randomly spawn in one of exactly two places instead of always being in the same place.


 * Some power-downs may be classified as “bad” but they can factor in to your strategy. For instance, picking up a “🔒” Lock Weapons orb at just the right time can help you power through a screen full of enemies, if you want to make sure your weapon isn’t auto-switched to anything else that might be floating by.


 * There are a lot of different weapon combinations to experiment with! Default weapons are not only attacks by themselves, they modify some other weapons; for instance, the attacks used by defenders like “Shadow” and “Trailer”, and the secondary attacks of certain weapons such as “Sideliner”.


 * The “Prism” defender pod drastically alters the trajectory of many weapons, to the point where they are almost entirely different weapons; experiment with these to find new methods of attack.


 * Some environments (such as space) change weapon behavior! For example, a weapon that naturally relies on gravity like “Ground Wave” will actually float in space, producing an entirely different attack pattern.  Try it!


 * Ship speed can be changed in multiple ways and this can be crucial for navigating tight areas.

Story
The game is set far in the future, when there is widespread colonization of space. This peaceful society did not prioritize having strong defenses. When unknown enemies suddenly appeared and launched vicious attacks, there were few options and time was running out. In a city far from combat, scientists experimenting with new sources of energy found something that could be rapidly repurposed for combat, using devices small enough to fit aboard a few jets parked at the facility. You now pilot one of these ships, and fight for survival.

(To see the game ending story, all stages must be completed in one run; while you can start at any stage, the game will loop back to the beginning until the rest are completed.)

Version Differences
The touchscreen versions of the game (iPhone/iPad) have onscreen controls, whereas on macOS/desktop and tvOS most information is only displayed as needed. The graphics quality is also much higher on the macOS and tvOS versions, more suited to large displays.

Trivia
The game logo on the options screen can be used to view the game introduction (and story) at any time.

Gallery
See Celtreos/Gallery for our collection of images and scans for the game.

Video References
Trailers of the game can be found on Steam and YouTube. See also Video Index.

References & Contributors

 * This page was created by the developer of this game, Kevin Grant.
 * Additional information on game weapons and power-ups: Celtreos Guides (on Steam).
 * General: Celtreos Help
 * Short videos: Celtreos YouTube Channel