After trudging through the snow for a week, brushing back border forces, the Soviets started running into stiffer resistance in their drives to outflank the main Finnish defenses 70 years ago this week.
At Suomussalmi in central Finland and Tolvajarvi near Lake Ladoga the Finns, with their ski troops and sissi tactics proceeded to stop, and then drive back the Soviet spearheads in what is the classic image of the Winter War -- outnumbered white-clad hardy Finns beating back hordes of ill-prepared Russians. Both locations are shown below in this map from the GURPS source book GURPS WWII: Frozen Hell, which provides an excellent overview of the war even if you don't play that role-playing game.
That image is certainly the impression most wargames would leave. The Tolvajarvi battle in particular has been a popular wargame topic with at least two comprehensive simulations being published.
Rarely shown in wargames are the grimmer, more conventional battle along the Mannerheim Line where the war was really decided. There's little glamour in bloody frontal assaults against grimly held fortified lines. The Soviets' December offensive failed.
The old SPI game Winter War does manage to show the true balance between the fronts. While there will usually be some entertaining and dramatic thrust and parry in the center, the game and the war will be decided around the Mannerheim and Ladoga lines in the South.