Using A container for Tanktop and Tankbottom will also make the creation, as you have done, more simple. Only have to create One of both, and the other gets auto created by the system in an urge to always have complete Containers.
I use Layers to Z-order simple orders like those.
lines 21 and up
I prefer to do the keys different,
On key M pressed, i would set 'weapon-selected" to "Landmine" as you already do. I would move all those key input triggers up in the sheet, so there are visible and noticeable. And just like you i would test 'weapon-selected' later on to take action. But you dont do this for the trigger "space is down".
I would also make a variable to go with the space bar action. Move it up in the sheet by the other key conditions. And test conditions based on the variable set to "fire" later on in the Sheet.
Now you use 2 systems
If you want to to limit key input in some stage of the game now. Then its not easy to keep the actions and sub events that go with the keys from executing. Especially because you use two systems at them moment. Different for space bar then the other keys.
Lines 35 and up.
You could use a family for all the different bullets here. Every Conditions has basically the same lines here.
See, if you use a family for the bullets, ..
The condition "On collision between family and Enemy" ...
Takes all the Family objects, (the bullets) ....
And will filter out all the bullets that are not colliding with enemy from that picked group ...
Then takes all the Enemy objects ...
Will filter out all the Enemy's that are not colliding with Family ...
And only the objects that pass the filtering go to the sub events and actions ..
If there is no collision then there is no object to pass to the sub events and actions, so there will be noting run ...
If there is a collision, the 2 objects involved in the collision will be passed to the sub events and actions, they will be set "picked"
If the action says "destroy family", not all the objects in the family will be destroyed, only those that are set as "picked", those that past the filtering.
I do love that TankTread, btw.
The Zap sound. Could it be. In event 56 you give the enemy tank a target.
And a little later in event 61 u tell it to zap when there is a target acquired ?
This all is not to break your creation down, you asked for an opinion.