The objective is to burn the monkey boss as many times as you can before you lose all 4 lives (the starting one plus 3 replacement robots indicated in top left corner). To burn the monkey, transfer 5 logs from the stack on the right to the furnace on the left. When you add 4 logs the fire will start blinking which is an indication to you that the next one will blast a fire through one of the three valves above. A small fire indicates where this will be and it always moves to the right every few seconds. When the monkey is exactly under the fire, add the fifth log and burn the monkey.
Each time you burn the fire, whether you hit or miss, the monkey will enter rage mode. While in this frenzy any pauses between throwing bricks in the usual behavior are skipped. Be careful on higher speeds and it's usually best to just wait until the rage is over before proceeding. Also use this time to clear the stack on levels 5 and 7 (described below).
Scoring and multipliers
You earn 1 point for each log you put in the fire and 50 for burning the monkey. Additionally, a multiplier is increased for each time you burn the monkey with perfect play. So with the highest possible x9 multiplier, adding a log is worth 9 points and burning the monkey gives you 450, blasting you through the levels of the game!
To keep the multipliers active you need to maintain perfect play. This means:
If you don't bring new logs to the fire, after a couple seconds, the furnace will drop power and reset your multiplier.
If a falling brick destroys your log while you are carrying it, you lose the multiplier.
If you miss the monkey with the burn on the 5th log, you lose the multiplier.
Dying in any way also gets you back to x1.
Clearing the stack
The game will end if you let the stack of logs on the right to fill up, no matter how many lives you have left. So proper stack maintenance is vitalwhen the alert siren starts blinking. Very fast play, especially the two finger technique described in the speedrun section can be of help to this, but another especially useful tactic is to stand next to the stack while the monkey drops bricks on you. Just repeatedly pick up new logs from the stack for your protection until you are ready to move on. This is most effectively done on levels 5 and 7 (described in next section).