Differences to X-COM (OpenXcom)

General

• None of these bugs or limits.
• Mouse wheel support.
• Caret for text editing.
• No CPU-based speed (animations play at a constant speed regardless of the computer).
• Mouse input works like modern systems.
• Human-readable savegame format.
• No savegame limit.
• Painless customizability with modular rulesets in human-readable format.
• Full Unicode support.
• Localized in many more languages.
• Take screenshots in-game.
• Standalone "Skirmish" style custom Battlescape mission generator.
• Customizable keyboard shortcuts.
• Native support for in-game music in many different file formats (including OGG, MP3, etc.)
• A built-in and extendable selection of optional display filters.

Geoscape

• Since there's no 80 item limit, items in crafts count towards your Base Stores to prevent exploiting infinite storage. This also lets you freely move items between bases and crafts without storage issues.
• Each radar facility contributes to the detection check, so having multiple Small Radar Systems and/or Large Radar Systems does improve your chances. The Hyperwave Decoder still makes all other facilities obsolete though since it has a 100% detection chance.
• The aircraft phase order when returning to base is: Repairing, Rearming, Refueling.
• Purchase/Recruit screens have a column for current storage.
• Aircraft weapons may be unequipped.
• Can cancel out of selecting armor for soldiers.
• Selling aircraft automatically unequips all their contents.
• No gap in Australasia zone.
• Soldiers can be reordered in aircraft.
• Aircraft and Bases can be renamed.
• Potential radar coverage will be displayed when placing a new base, and can be toggled at any time with the press of a button.
• Aircraft will use proper great circle calculations when travelling to waypoints/targets.
• Night/Day line is dithered slightly.
• Right-Click will center the camera on a point on the globe.
• Mouse Wheel will zoom in and out.
• The initial base setup can be the same, or optionally, manually laid out as you see fit.
• By enabling a config option, live aliens can be sold.
• UFOPaedia articles regarding Aircraft weapons have flavour text (unused strings existed in the original were implemented)

Battlescape

• Right-click opens doors.
• Right-click will cancel a unit's movement, and will cause projectiles to "skip" their flightpaths, instantly hitting their target.
• Objects, fire and smoke keeps animating while walking or scrolling the screen.
• Pathfinding is a different algorithm: it will always find a solution, if there is one, no matter how difficult.
• AI of aliens is more cunning - Impossible to 100% exactly mimic original AI.
• Waypoint-based projectiles have no upward limit on the number of waypoints they may use.
• The CTRL key may be used to "force fire" when no line of sight is available.
• The inventories of mind controlled, non-terrorist aliens may be accessed.
• The limit on units has been removed, allowing 23 or more soldiers to assault alien bases.
• Unit spawning function has been improved - no more large units stuck in walls.
• Units holding two single-handed weapons will have the fact represented on their sprite.
• Soldier sprites will have their hair and skin recolored to represent their race.

Optional features

While the above differences are hardcoded, there are also various new "non-vanilla" features you can choose to enable. See the Customizing section for more information.