Rules of the PV Graph:
• Area under the curve: Magnitude of Work.
• Volume expands: Gas does positive work (Work ON gas is Negative).
• Volume compresses: Surroundings do positive work (Work ON gas is Positive).
• Temperature shifts: Isotherms (constant T) are hyperbolas $P = nRT/V$. Moving to a higher isotherm (up and right) means positive $\Delta U$.

Positive Work, because pressure increases. Negative Work, because energy leaves. Zero. $W = -P \Delta V$. With no change in volume, there is absolutely zero work done.