chore: doc & expose TickModulator trait, rename speed to tick

src/modulation.rs

@@ -1,22 +1,44 @@
-pub struct SpeedModulator {
+/// A tick modulator allows you to slow down operations by a percentage.
+/// 
+/// Unfortunately, switching to floating point numbers for entities can induce floating point errors, slow down calculations
+/// and make the game less deterministic. This is why we use a speed modulator instead.
+/// Additionally, with small integers, lowering the speed by a percentage is not possible. For example, if we have a speed of 2,
+/// and we want to slow it down by 10%, we would need to slow it down by 0.2. However, since we are using integers, we can't.
+/// The only amount you can slow it down by is 1, which is 50% of the speed.
+/// 
+/// The basic principle of the Speed Modulator is to instead 'skip' movement ticks every now and then.
+/// At 60 ticks per second, skips could happen several times per second, or once every few seconds.
+/// Whatever it be, as long as the tick rate is high enough, the human eye will not be able to tell the difference.
+/// 
+/// For example, if we want to slow down the speed by 10%, we would need to skip every 10th tick.
+pub trait TickModulator {
+    fn new(percent: f32) -> Self;
+    fn next(&mut self) -> bool;
+}
+
+pub struct SimpleTickModulator {
     tick_count: u32,
     ticks_left: u32,
 }
 
-impl SpeedModulator {
-    pub fn new(percent: f32) -> Self {
+// TODO: Add tests
+// TODO: Look into average precision, binary code modulation strategy
+impl TickModulator for SimpleTickModulator {
+    fn new(percent: f32) -> Self {
         let ticks_required: u32 = (1f32 / (1f32 - percent)).round() as u32;
 
-        SpeedModulator {
+        SimpleTickModulator {
             tick_count: ticks_required,
             ticks_left: ticks_required,
         }
     }
 
-    pub fn next(&mut self) -> bool {
+    fn next(&mut self) -> bool {
         self.ticks_left -= 1;
 
+        // Return whether or not we should skip this tick
         if self.ticks_left == 0 {
+            // We've reached the tick to skip, reset the counter
             self.ticks_left = self.tick_count;
             false
         } else {