write some TODO comments

src/game/tetromino/placing.c

@@ -62,6 +62,7 @@ static void set_shape_i(row const* const row, u8 const id, int8_t const pos_x) {
 	colour8 const colour = colour_from_id(id);
 	for (int8_t y = 0; y < SHAPE_HEIGHT; y++) {
 		u8 const shape_row = shape_get_row(shape, y);
+// TODO: this is suboptimal, ditch the entire "representing shapes as binary-formatted data" and instead use a switch...case.
 
 		if (shape_row == 0)
 			continue;

src/io/audio.c

@@ -1,3 +1,4 @@
+// TODO: audio stores audio buffers at indicies that the user specifies. (array growth is the next power of two from the idx)
 #include "audio.h"
 
 #include <SDL_audio.h>

src/io/input.c

@@ -5,6 +5,7 @@
 
 #include "window.h"
 
+// TODO: this'll likely be insufficient, due to no code delays being applied, or it registers *just* the keydown event
 __attribute__((const)) static int procscancode(SDL_Scancode code) {
 	switch (code) {
 	case SDL_SCANCODE_Q: return MOVRL;

src/io/render.c

@@ -84,6 +84,7 @@ static void draw_score_text(renderdata const* dat) {
 	SDL_RenderCopy(renderer, cache->score_texture, NULL, &text_rect);
 }
 
+// TODO: this is suboptimal, since each block will be 2 triangles, wasting perf. Consider using switch...case hard-coded drawing
 // draws a block at the specified position
 static inline int draw_block(SDL_Renderer* const renderer, int8_t const x, int8_t const y) {
 	SDL_Rect const block = {get_column_pos(x), get_row_pos(y), BLOCK_WIDTH - 1, BLOCK_HEIGHT - 1};