hard

It works. Barely.
The old man's weapon only works by pivoting his bent arm around the shoulder.
This means getting in close enough that the enemy can hit back, and makes a strike and retreat strategy difficult to implement.

Could definitely use another joint at the elbow, and probably the wrist also.
This would allow for thrusts with more range.

The size of this might work well on the phones, but is a bit large on the PC.
Also: the game "captures the mouse" and makes it difficult to move the mouse off the play area without refreshing the page.

No sound? Not much of an issue, but some people need to have their noise to enjoy a game.
I'd suggest you put in some music for each of the screens "to set mood".
Layer on top of that some "ouch" or otherwise "hit" indicators for those who need them.

A sword being drawn from a scabbard at the start of battle could be another nice sound effect.