The Arena is a room. "Sand, blood, iron. These festivals are normally held on hot days, but the sun has gone behind a cloud and fat drops of rain now and then spatter the arena floor." The gladiator is a man in the Arena. "A bare-chested Scythian gladiator faces you, wielding a trident."
We start by recording, for each person, a maximum number of points of damage the person can sustain when starting from health, and the current number of points remaining. In the tradition of role-playing games, these are referred to as hit points.
{**}A person has a number called maximum hit points. A person has a number called current hit points.
The maximum hit points of the player is 35. The maximum hit points of the gladiator is 25.
Now our rule for the actual attack. We want first to calculate how much damage the player's attack does, inflict that damage, and remove the enemy if they're dead; then, if still alive, the enemy counter-attacks, also for a randomized amount of damage, and if this kills the player, the game ends in defeat.