Sword Knight is an action RPG: you fight through enemies with a sword, collect what they drop, and spend it on equipment that makes the next area survivable.
The gear progression is the point — an area that's impossible now becomes routine two upgrades later, which gives the grinding a purpose.
An action RPG — real-time combat with gear progression rather than turn-based battles.
Weapons. Higher damage shortens every fight, which reduces the total damage you take more than extra armour does.
Yes — it runs in the browser with nothing to install.