They shall not pass. Toy Defense 2 returns offering 72 levels of classic tower defence gameplay

Although it's not been fashionable for a while, tower defence never goes out of style.

And it's a genre that's certainly been successful for Russian developer Melesta.

So following the multi-million downloads of its original Toy Defense release, the sequel has hit the App Store.

Thematically, it's an interesting mixture of toy soldiers meets World War II locations and unit types.

Each of the three map packs (each containing 24 maps) covers one element of the European war; Stalingrad, D-Day, and the tank battles of Northern Africa.

Gameplay-wise, Toy Defense 2 offers creativity through restrictions.

A single-player game, it only has four unit types: rifleman, artillery, anti-aircraft and air interceptors, and on the map, each type has specific locations where they can be placed.

Should a unit been destroyed, you can't reuse that location, unless you have a respawn item.

Deeper variation is provided, however, as each unit can be upgraded, including via six-way technology tree.

For example, you can improve your rifle unit's chances of an instant kill, or slow down vehicle movement as you unlock these abilities.

In terms of the attackers, these come down fixed paths, and as you'd expect, as you destroy them, the money you collect is used to generate more defensive units, or repair and upgrade those in-use.

Also, neatly, at the end of each battle, you can choose some of your units to take into the next battle - a sort of Hero system, even if the units themselves are generic.

Another interesting design decision by Melesta is the way it uses the in-app purchasing system.

Although Toy Defense 2 is a paid game, there are the usual soft and hard in-game currencies, which allow you to speed up your progress if you're prepared to shell out some cash.

Soft currency is used to access the units' update tree, which hard currency buys you single-use items.

However, there's no in-game store. Instead, you're offered purchases between levels, when you have the option of upgrading units, or via occasional in-game email prompts.

Alternative options for getting currency include interacting with Melesta on Facebook and Twitter.

Out now for iPhone ($1.99/£1.49) or in an HD version for iPad ($4.99/£2.99), Toy Defense 2 is also coming to Android.