Reading the original competition thread helps. You can even download wolfmame 1.06 and watch a .inp replay of the 1.5 mil score.

Basically you go for a horizontal five in the middle, sandwiched by four vertical fours left and right, leaving the vertical column in the middle half empty.

Example:

red blue green yellow

red blue green yellow

orange orange orange orange

red blue yellow green yellow

red blue yellow green yellow

If you drop an orange tile in the middle, the horizontal five collapses and you get four vertical fours.

Ideally, if you have two orange tiles in the vertical middle column and drop the final orange tile, you also clear the pit completely. This nets you about 200-265k.

Very ideally, you can drop tiles even as the klaxs are vanishing, so in this example if you drop an orange tile followed very quickly by two yellow tiles, you can get a horizontal five and five vertical fours, cleaning the pit completely. This nets you about 300k.

BUT there is a caveat, because if you take too long to clear the level, the next level gets harder. Thus far I haven't been able to clear the 40 tile level because the tiles move too fast. And also because I suck at the game.