In the early stages the gameplay of Immortal Defense is similar to what you would expect from any tower defense game. New points are gradually introduced, giving new forms of offense which can be used to encounter a constantly growing roster of foes. The game does not stay static, however, and it constantly introduces new concepts as the levels progress. The points, which act as a tower or turret would in a more typical tower defense game, can be used in combinations that make them more and more powerful. For example, the Turning Point can be used to make other points fire on opponents in directions which would normally be impossible These combinations are made more important by creative level design. Every level is essentially a path between one point and another, but these paths are created so as to provide many strategic opportunities.
Immortal Defense also side-steps some of the genre's classic faults. One of these is the possibility of the player building themselves into an impossible situation, a problem which in turn can ruin the pace of a tower defense game. This problem is vanquished in Immortal Defense by the use of numerous shorter levels. Individually, each one takes only three or four minutes to complete, which means that it isn't a big deal to start over again if a strategy appears hopeless. This in turns gives Immortal Defense room to be more challenging. As the levels progress, the paths become accompanied by numerous obstacles as well as a variety of enemies, each with their own strengths and weaknesses. Immortal Defense is not a game that wishes to take long walks in the park, and as the levels move forward it becomes quite difficult. Unlike some tower defense games I've played recently, it does not go out of its way to point out successful strategies. Some of the boss fights can seem virtually impossible at first glance. But as with all good puzzles, these levels can be unraveled through creative usage of the tools at hand, and there are few things more satisfying than conquering a level you originally thought unbeatable.