One of the biggest issues with playing Lego Island on a modern computer is its turn speed.
Lego Island infamously ties its turn speed to its running frame rate, which means the faster the game is running, the faster the turn speed will be. The computers of the era would render Lego Island at approximately ~10 FPS, but modern systems have no trouble and will happily run at the game's fixed limit of 90 FPS. This causes turning to be 8-10x faster than intended and makes maneuvering often unwieldy or even unplayable.
This is even a known issue according to the developers, only discovered once higher powered computers were tested at the end of Lego Island's development . A fix was even written, but never released as either a retail update or as a downloadable patch.
Internally, turn speed is a 32-bit float with a range of -20.0f to 20.0f (-20.0f being left, 0.0f being no turning, and 20.0f being right). Lego Island's mouse control (clicking and dragging on the screen) will utilize the full extent of this range (far left side being -20.0f, far right side being 20.0f, and a float in that range in between), but keyboard controls push all the way to each extreme, i.e. as fast as the speed was designed to go.
This 20.0f value is hardcoded as the maximum turn speed into LEGO1.DLL. Lego Island Rebuilder patches the game to run the value through a second multiplier of the user's choosing. Essentially the user can change the turn speed to whatever they want (it can even increase the turn speed, however this is obviously not recommended).