The system is called "Triangle" because the grid on the board consists of equilateral triangles. The vertices of these triangles are to be perceived as spaces the pieces use to move.

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The main characteristics of the Triangle system is that one piece represents one vehicle (a plane, a tank, a ship...) and each of them moves individually. In this system, the position of a piece isn’t the only important thing, but also their direction (it depends on the space – vertex – from which the piece came).

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The game mechanics are simple – the player rolls dice (one or more depending on the game) and moves one or more pieces on the board. If some piece is in a position to shoot (fire a gun, missile, etc.) – the player rolls a die again to determine if it is a hit or a miss. All these characteristics - speed, range, power, etc. - are interrelated and well-balanced so that we get a realistic battle game that’s still very simple to play.

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There are two main subsystems of movement that apply to any moving element. One is applied mostly for slow vehicles, and those that can rotate in place. The other is for fast moving vehicles and flying crafts (planes, helicopters etc.). Besides movement, some actions like "shooting" also use the second movement system - movement of launched missiles, torpedoes etc.

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https://boardgamegeek.com/boardgamefamily/26759/triangle-system