The genre
What is an incremental tower defense game?
An incremental tower defense game is a tower defense game with the progression of an incremental (idle) game: you place defenses to stop waves of enemies, and every wave pays into upgrades that make the next attempt stronger, so your power keeps climbing across many runs.
Tower defense, briefly
In a tower defense game, enemies come in waves toward something you must protect, and you stop them by placing defenses (towers, soldiers, traps) where they will do the most good. You earn resources for every enemy you stop and spend them on more and better defenses. A classic tower defense level is a puzzle you solve once: you win it or you lose it.
What the incremental part adds
- Losing still pays. Part of what you earn is kept when a run ends, and spent on permanent upgrades.
- Numbers that compound. Upgrades multiply each other, so each attempt goes further than the last.
- Prestige. Resetting on purpose, in exchange for a bigger, permanent bonus, so the next climb is faster.
- Automation. The game can run waves on its own, which is where the "idle" in idle tower defense comes from.
- A long horizon. Instead of a set of levels, a climb measured in hours or weeks.
Idle or incremental?
Close, but not quite. "Idle" puts the weight on automation: the game keeps fighting, and often keeps earning, while you are away. "Incremental" puts it on compounding growth: permanent upgrades, prestige resets and numbers that climb. Most games in the genre are a bit of both.
Examples of the genre
The genre is broad. A few well-known games from it, as their makers describe them:
- The Perfect Tower II: a mix of an incremental and a tower defense game with idle elements, with a town to build and regions to explore.
- Idle Tower Defense: start with a simple tower, choose modules and beat waves for points.
- Zero Stress King: Idle Defense: a short, relaxing incremental game dressed as a tower defense.
Where Marrow March fits
Marrow March is a free incremental tower defense game that runs in your desktop web browser: you raise an army to hold the last wall against a skeleton horde, grow it through hundreds of upgrades, and climb ten ages of the dead. Its towers are soldiers you place and train (archers, wizards, catapults, shamans, windcallers and ballistas), and its twist is the wall: when the dead breach it, the run does not simply end. The fight moves inside, onto the road to the city gate. Around that sits the incremental loop: Essence kept between runs for 351 permanent upgrades, a prestige layer called the Ancestral Sky, AUTO assaults for idle play, and 10 ages to climb.
About Marrow March · How to play · The wiki
Questions
What is an incremental tower defense game?
An incremental tower defense game is a tower defense game with the progression of an incremental (idle) game: you place defenses to stop waves of enemies, and every wave pays into upgrades that make the next attempt stronger, so your power keeps climbing across many runs.
Is an incremental tower defense game the same as an idle tower defense game?
Close, but not quite. "Idle" puts the weight on automation: the game keeps fighting, and often keeps earning, while you are away. "Incremental" puts it on compounding growth: permanent upgrades, prestige resets and numbers that climb. Most games in the genre are a bit of both.
Is there a free incremental tower defense game in the browser?
Yes: Marrow March is a free incremental tower defense game that runs in your desktop web browser: you raise an army to hold the last wall against a skeleton horde, grow it through hundreds of upgrades, and climb ten ages of the dead. It is in a closed test now, and the free demo opens to everyone in October 2026.