better tutorial UI

[iznaut]

the UI for teaching the player what keys do what continues to be an unruly beast - i think there's a lot of room for improvement here.

my take is that controls should be more integrated with the environment. Spelunky does a great job with this in its tutorial, with big signs in the background displaying controls as they're needed (i think we need a proper tutorial level to really do this well, but even just making the existing text a sign behind the player would be a huge step forward imo)

also, actions that are context sensitive should be displayed as such - a good example is the "fireball" powerup. there is no need for the player to know about that keybind until they pick up the item, at which point the game would display a little "press B" popup for a few seconds before fading out. i don't have a good reference on hand for this, but i bet there's a lot of helpful stuff to look at here: https://www.gameuidatabase.com/index.php?&set=1&tag=25&scrn=907&scroll=58

these are good short term fixes, but long term a few things that would be helpful:

• better gamepad support (e.g. WASD replaced with D-Pad/Left Stick icon where relevant when gamepad is plugged in)
• hidden controls while on mobile (or simplified - since touch buttons are always present on-screen, there's no reason to tutorialize)
• input mapping reference in pause menu (see all currently relevant controls for the given scene)

[nknauth]

Partially addresesd by #372