Up & add'em!

Up & add'em! is a 1976 uncredited game, published at Aladdin.

The game is played on a central 9x9 area, with an outer layer where the pieces start.

Each player has nine pieces labelled from 2 to 4 (four 2s, three 3s and two 4s). These are stackable pieces. A stack ownership and move range is determined, respectively, by the top piece's color and label.

Rules

• Initially, players setup their nine pieces in any order they like.
• On his turn, the player moves one of his stacks.
• A stack moves the number of steps given by his label, going thru empty positions or even jumping over other stacks (each step costs one unit of movement).
• Stacks move orthogonally, and can change direction during their movement.
• Stacks can stop on top of enemy stacks, provided that (a) the final size of the two stacks together is four or less pieces, (b) the top piece of the moving stack is greater or equal than the top piece of the captured stack.
• The game ends when no more captures are possible. 
• A stack value is the sum of all its pieces 
• The player with the highest score wins the game 

The official rules:

I'm not so sure that the end condition is obvious to check in every situation. It is easy to verify that one player cannot capture enemy stacks (given the remaining numbers of their stacks with less than four pieces). But if, say, both players have one remaining stack of size two with a top-piece labelled 2, what happens then? Can one trap the other? I'm not so sure about that. Probably an extra stop condition is needed. Something similar to Chess, that after N turns without captures the game does end.