Heat Man
Heat Man Screen 1
Most of this screen is trivial - hold right and shoot enemies.
The Item 3 Throw Section
Switch to item 3 after walking off the high platform. Pause and switch to item 3 here - pausing itself (even without switching weapons) resets the falling speed so you reach the lower platform.
The item 3 throw is rather precise. The backup is to instead switch to item 2, or just platform normally.
Heat Man Screen 3 - Part 1
Zipping
Do not drop off the ladder when entering screen 3. You can hold down in the screen transition to grab the ladder if you press A to drop down the ladder. (You can also set up the zip from the floor, but it takes several more seconds.)
There is a very specific placement of item 3 from the ladder, against the left wall, for the optimal setup.
Stand on the left edge of the item 3, so Mega Man is mostly under the ceiling, not the ladder gap. Wait for Mega Man to suddenly move above the screen, then execute the A-Trigger Zip (https://goodboyrush.net/books/mega-man-2/page/zipping )
Zipless
The strategy for Zipless relies on using Item 2 as a platform, while keeping enough energy left over to fly across the disappearing block gap (in screen 3 part 2).
Heat Man Screen 3 - Part 2
This covers the long disappearing block portion of Heat Man's stage.
With Item 2
If you are playing Zipless, or did Air second, you will have item 2. Walk along the bottom up to the lava, then use item 2. Depending on how much energy remains, you may need to jump near the end.
Note that while this is the fastest (and safest) method for Heat Man's stage itself, in a Zips route, it is slower overall than doing Heat Second and then "Fast Air" using Item 1.
Without Item 2 (Heat Second)
Typically this only comes up for with Zips and Heat second, or for challenge runs (such as buster only), although in a race scenario this may be needed if you had an accident.
The blocks spawn starting from when their X coordinate appears on the screen, so always be moving to the right.
Get to the Lava pipe, and stand on the left edge of it facing right. You will need to time the jump so Mega Man is "in" the block at his highest point. The appearing block will place Mega Man on top of it as it appears.
In progress