Every game on this shelf asks the same question and answers it differently: something is coming down a road, and what are you going to put in its way? The difference between them is whether you spend money, men, or your own two hands.
Crown Hold is the true tower defense of the four. Raiders walk the road, you raise what stops them, and the decision is always the same shape - spend now on the wave in front of you, or save for the one you can see coming. Gatecrash inverts it: you are the thing coming down the road, firing an army up a single lane while a garrison spends its own men to meet you.
Swarm Cannon is the arithmetic version, where the gates your crowd passes through decide the fight before it starts. Riot Line takes the tower out entirely and makes you the wall: punch the quick ones, kick the shielded ones, and do not let the line behind you break.
None of them has a campaign to grind or a currency to buy. A run is a few minutes, the difficulty comes from the waves rather than from a paywall, and they all open in a tab.
