Release blocker!: Fix the collision detector to work with Level 2 and above

[DiddiLeija]

First pointed in #3, this is a critical issue that must be addressed as soon as possible.

[DiddiLeija]

I'm currently trying to fix the "collision detector" directly on the function (see e2b1087), but seems to be trickier than it seems :/

[DiddiLeija]

Oops, a93b489 closed this accidentally :/

[DiddiLeija]

I've made a few changes to the way I work with the y-level on levels from 2 and above.

Previously, it worked a bit like:

treat everything like if we're on y=0, but both {LEVEL_NAME}.draw() and detect_collision() (and related functions) have to make adjustments to work as expected

Honestly, making this has become a little tricky, so I adopted a new focus:

Notify the Player and mob classes which is the top y value on this level (and then, the bottom value is y + 120 instead of just 120), and act normally ignoring that y != 0.

Hope this new method works better 😓

[DiddiLeija]

Fixed! 🎉