general:

- try to remove the debug flag (-g1) from compiler and see if it decreases size
- port to GB Meta
- more level prop items
- sounds (music?)
- level 2D map (with revealing, bitmap), special key for quick displaying map
- save/load (optional)
- more levels
- disable transparency for walls for performance (setting)?
- replace textures in distace with constant color for performance (setting)?
- add time slowdown constant
- if space left, try blurring (lerp) the level background, see how it looks
- some monsters could reflect plasma, i.e. not be hurt by it, but reflect it
  back towards the player
- compile with different compilers (gcc, clang, musl, ...) and settings, make
  a build script that creates multiple binaries (with different combinations of
  compilers and settings)
- run on raspbery pi
- add jump pads?
- add robot deactivator item? (encourages "stealth" gameplay)
- add "pletivo" transparent wall texture?
- add universal corpse sprite?
- easter egg(s)

level ideas:

- wall made of elevators (or squeezers), serving as a big auto-opening gate
- a key spot to which the player can only get by jumping from a distant high
  elevated place
- player has to jump from one elevator to another, which can only be done when
  they're both moving down
- multiple doors in a row (can look interesting)
- narrow (1 square wide) corridor filled with enemies blocking it
- narrow (1 square wide) corridor blocked by barrels that have to be exploded
- teleport on elevator?
- teleport at the bottom of a 1 square narrow hole, by jumping into the hole
  the player gets teleported
- narrow corridor with elevator
- maze from walls and/or props
- narrow bridge with platformer elements over a hole full of enemies
- server room
- window (low unpassable ceiling) through which finish can be seen from the
  start location of the level
- three locked doors in a row at the beginning of the level, the player has
  to go to three different locations for each key -- a "hub" level
- office building
- plasma bots guarding a big stock (store) of plasma ammo
- warrior (enemy) right before the player at the start of the level
- T-shaped corridor in which two rocket-firing enemies stand facing each other
  so that the player can kill them by stepping between them, letting them fire,
  then stepping back, making them kill each other
- enemy trapped between barrels
- teleport that leads to another teleport which is on a single high elevated
  square from which the player has to jump down and won't be able to return,
  making it a de-facto one-way teleport
- teleports placed so that the player can shoot himself with a rocket or plasma
  (for fun)  
- exploders in a maze, hiding behind corners
- teleport leading to a center of big room full of enemies
- easter egg -- a level that looks funny on the map, e.g. forms a text or a
  picture
- squeezers with low-elevated base (a hole), on a side of a corridor -- if the
  player is curious and jumps in, he's doomed to die -- perhaps there can be
  many of them while one is in fact an elevator, which the player has to spot
  and take in order to advance
- bullet-shooting enemies behing windows (low ceilings) in rooms that can't be
  reached
- locked door that cannot be unlocked at the beginning of the level as a
  visual indication of entrance
- elevator in a narrow (1 square) vertical hole with doors at the top and
  bottom, looking like an actual elevator in buildings
- player goes through a difficult platformer section and at the end has to make
  a choice between going to the left and right by jumping in either direction,
  takes card and has to go through the whole section again in order to also
  take the other one
- big platform made of elevators that moving in a short vertical distance,
  giving an impression of a shaking, unstable platform
- warrior and/or exploder right behing doors
- tight maze made of barrels filled with warriors in which the player has to
  only use knife in order not to explode the barrels and hurt himself
- enemy on an elevator that doesn't stop at aligned with the floor, so that
  the enemy is "trapped" on it and only appears briefly to shoot at the player
- barrel on elevator
- platforming vertical section in which the player is going upwards out of a big
  hole
- invisible bridge (perhaps not straight) made of bleckers (invisible walls)
  over a hole, leading to an easter egg
- start of level: a corner blocked by an invisible wall, to indicate entrance

bugs:

done:

- add headbob
- make zBuffer 8bit only?
- texture coords of floor walls should start from the floor? NO, CAUSES ISSUES
- vertical visual noise when standing on elevator
- sprite positioning inccuracy
- try to compress images: store images as 4 bits per pixel + 16 color palette
  (subset of the 256 color palette), check if performance stays ok
- custom font
- make barrels explode.
- enemies
- weapons
- create tables for monster and weapon stats in constants.h and read from that
  instead of cheking with ifs
- check if monsters are hit by bullets from completely up close
- menu
- GUI
- make enemies not move through items:
  create a 2D bit array saying at which squares there are colliding items, then
  check collisions for both player and monsters against this array (elevate
  these squares for collisions only) -- will also be faster