Ironhide Game Studio may be a little too generous toward its customers. The developer has been drip-feeding free updates to its hit tower-defense strategy title Kingdom Rush (Flash, iOS) for months now, extending its longevity with new gameplay and bonus levels. With a game that keeps on giving, will the audience care about or be willing to purchase a sequel?

The beloved original has an average iTunes rating of five-out-of-five stars from more than 24,000 users, so we’re gonna confidently say, “Heck yeah.” The sequel, Kingdom Rush: Frontiers, is due out soon: this spring for iOS and later for Flash. The concept hasn’t changed — keep the steady stream of enemy troops from exiting each level by peppering their path with turrets and other defense-based buildings. But the enemies, the heroes, and, most importantly, the (upgraded) towers have.

Here’s a sneak peek at what Frontiers will offer:

The towers

Strangely, the developers decided to stick to the same four base buildings from the original game: Barracks (pumps out foot soldiers to fight and block enemies on the ground), Archers (houses ranged bowmen), Wizard (has mages that cast spells from a distance), and Artillery (fires explosives that do area-of-effect splash damage).

After you upgrade these towers a few times, however, you’ll see the new structures that are specific to Kingdom Rush: Frontiers.

Barracks upgrade 1: Assassin’s Guild

The Assassin’s Guild produces — what else? — assassins. They can wait in ambush, invisible until they’re ready to strike.

Special upgrades:

The ability for assassins to rob enemies of gold that you can spend on your own fortifications.

A dodge maneuver that includes a counterstrike.

A special attack that does extra damage.

Barracks upgrade 2: Knights Templar

The alternate barracks upgrade to the Assassin’s Guild is the Knights Templar, which produces high-defense foot soldiers similar to the knights from the original game’s Holy Order castle.

Special upgrades:

Increased maximum health.

A chance to automatically revive when killed.

A special critical hit that cuts a vital artery, causing the foe to bleed and drain health for a bit.

Archers upgrade 1: Crossbow Fort

Instead of the rangers and musketeers from Kingdom Rush, Frontiers offers up crossbow-wielding snipers that offer a balance of speed and range.

Special upgrades:

Crossbowmen shoot a steady stream of bolts.

A falcon that increases the range of this and other nearby towers.

Archers upgrade 2: Windwalkers Totem

The second possible Archers building contains tribesmen who throw axes. These don’t travel as fast or as far as crossbow bolts, but they have a chance to stun enemies.

Special upgrades:

Hits can cause enemies to take extra damage from all attacks.

Dispels magic in the area and prevents enemy mages from casting spells.

Wizard upgrade 1: Necromancer Tower

Necromancers can take downed enemies and raise them as undead that fight on your side.

Special upgrades:

Necromancers can create a cloud of pestilence that will slowly damage enemies.

They can also summon a Death Rider that will attack enemies and boost the strength of allied undead troops.

Wizard upgrade 2: Archmage Tower

Archmages can store up their power when idle and then release up to three deadly bolts at once. If any kill an enemy, the remaining bolts will track and go after other nearby foes.

Special upgrades:

Slain enemies explode, damaging others around them.

A tornado that can run down the parade of enemies.

Artillery upgrade 1: Battle-Mecha T-200

This building is actually a launch pad for a mobile mech that shoots explosive artillery.

Special upgrades:

The mech lays down oil that will slow anyone passing through.

A volley of long-range missiles.

Artillery upgrade 2: DWAARP

The Drilling Weaponized Auto-Attack Rumble Platform (DWAARP) creates localized earthquakes to damage enemies marching next to it.

Special upgrades:

Fire damage.

A special drill attack that is a one-hit kill.

The heroes

Like in Kingdom Rush, you’ll get a few hero characters for free in Frontiers, but the rest will be paid downloadable content. Unlike in the original game, however, these new unique units have persistent stats, meaning you can slowly upgrade them over time (similar to the skill/tech tree that contained long-term bonuses that you can unlock in the first KR).

Here’s a preview of three of the new characters, along with their new skills and powers, straight from the developer:

Alric the Warrior

One of the best warriors in Hammerhold, Alric makes fighting a form of art. His discipline and training allows him to strike with lightning speed while also calling upon warrior spirits from the desert to aid him.

Primary skills:

Swordsmanship (passive): improves attack damage by 3/9/18 points. (Improves Flurry damage.)

Better Armor (passive): increases base armor by 10/25/50 percent.

Toughness (passive): increases hero life by 30/60/90 points.

Flurry (cooldown: 8/7/6 seconds): special maneuver that strikes its opponent 4/6/8 times in quick succession.

Sand Warriors (cooldown: 10 seconds): summons 1/2/3 sand warriors with 50/75/100 life to aid him in battle for 8 seconds.

Secondary skills:

Alric has a 20 percent chance of stealing some gold on every attack.

Mirage the Assassin

A legendary assassin of the order, Mirage has sworn her daggers and her unorthodox but effective tactics to the protection of Hammerhold and the forces of good.

Primary skills:

Precision (passive): improves ranged attack damage by 2/6/10 points.

Shadow Dodge (passive): grants a dodge chance of 40/50/60 percent and when dodging, leaves a copy of herself to fight for 1 second.

Swiftness (passive): increases movement speed by 10/20/30 percent.

Shadow Dance (cooldown: 7 seconds): summons 2/4/6 copies of herself that run and attack nearby enemies, dealing 32 damage each, and then vanish.

Lethal Strike (cooldown: 15 seconds): Mirage backstabs her target for 120/240/360 damage with a chance of slaying it outright.

Secondary skills:

Mirage becomes hidden when not attacking.

Cronan the Beastmaster

A son of the wild, a king of the jungle! He has fought on every terrain known to man, his whip has tamed beast and man alike, and with him comes the unstoppable wrath of nature.

Primary skills:

Boarmaster (passive): summons two boars with 80/160/240 life that attack and block enemies in range.

Stampede (passive): calls on a rhino stampede that deals 30/60/90 damage to every enemy caught in its path.

Falconer (passive): trains 1/2/2 falcon companions that attack enemies in range for 20/40/60 damage every 5 seconds.

Deep Lashes (passive): attack that deals 40/80/120 damage and bleeds the target for 60/120/180 damage over 6 seconds.

Regeneration (passive): regenerates 5/10/15 hit points every second.

Secondary skills: