fix atan issue

the love2d that I'm using doesn't have the new atan arity lol

asteroids/main.lua

@@ -1,5 +1,6 @@
 local love = require("love")
 local phys = require("phys")
+local inspect = require("inspect")
 
 local function initGame()
     return {
@@ -51,7 +52,7 @@ local function initState()
         }
     }
     for _, asteroid in ipairs(asteroids) do
-        asteroid.angle = love.math.random() * (2 * math.pi)
+        asteroid.angle = love.math.random() * phys.tau
         asteroid.stage = #game.asteroids.stages
         local stage = game.asteroids.stages[asteroid.stage]
         asteroid.speed = stage.speed
@@ -65,11 +66,9 @@ local function initState()
         ship = {
             x = game.width / 2,
             y = game.height / 2,
-            angle = 3 * math.pi / 2,
-            speed = {
-                x = 0,
-                y = 0,
-            },
+            angle = 0,
+            facing = phys.tau * 3 / 4,
+            speed = 0,
             radius = game.ship.radius,
         },
         bullets = {},
@@ -100,14 +99,14 @@ end
 function love.update(dt)
     if state.controls.joystick ~= nil then
         local thrust = state.controls.joystick:getGamepadAxis('triggerright') * game.controls.ship.maxThrust
-        state.ship.speed.x = state.ship.speed.x + math.cos(state.ship.angle) * thrust * dt
-        state.ship.speed.y = state.ship.speed.y + math.sin(state.ship.angle) * thrust * dt
+        if thrust > 0 then
+            phys.apply(state.ship, { speed = thrust * dt, angle = state.ship.facing })
+        end
 
         local spin = state.controls.joystick:getGamepadAxis('leftx') * game.controls.ship.turnRate
-        state.ship.angle = (state.ship.angle + spin * dt) % (2 * math.pi)
+        state.ship.facing = (state.ship.facing + spin * dt) % phys.tau
     end
-    state.ship.x = (state.ship.x + state.ship.speed.x * dt) % game.width
-    state.ship.y = (state.ship.y + state.ship.speed.y * dt) % game.height
+    update(state.ship, dt)
 
     for bulletIndex = #state.bullets, 1, -1 do
         local bullet = state.bullets[bulletIndex]
@@ -159,7 +158,7 @@ function love.update(dt)
     end
 
     if #state.asteroids == 0 then
-        reset()
+        --reset()
     end
 end
 
@@ -169,10 +168,11 @@ function love.gamepadpressed(joystick, button)
     end
     if button == "b" then
         -- debounce, perhaps
+        -- include ship velocity, perhaps
         local bullet = {
-            x = state.ship.x + math.cos(state.ship.angle) * game.ship.radius,
-            y = state.ship.y + math.sin(state.ship.angle) * game.ship.radius,
-            angle = state.ship.angle,
+            x = state.ship.x + math.cos(state.ship.facing) * game.ship.radius,
+            y = state.ship.y + math.sin(state.ship.facing) * game.ship.radius,
+            angle = state.ship.facing,
             speed = game.ship.bullet.speed,
             radius = game.ship.bullet.radius,
             timeLeft = game.ship.bullet.time,
@@ -180,8 +180,11 @@ function love.gamepadpressed(joystick, button)
         }
         table.insert(state.bullets, bullet)
         bullet.sound:play()
-        state.ship.speed.x = state.ship.speed.x + math.cos(state.ship.angle) * game.ship.bullet.recoil
-        state.ship.speed.y = state.ship.speed.y + math.sin(state.ship.angle) * game.ship.bullet.recoil
+        --state.ship.speed.x = state.ship.speed.x + math.cos(state.ship.angle) * game.ship.bullet.recoil
+        --state.ship.speed.y = state.ship.speed.y + math.sin(state.ship.angle) * game.ship.bullet.recoil
+    end
+    if button == "x" then
+        print(inspect(state.ship))
     end
 end
 
@@ -195,7 +198,7 @@ function love.draw()
             love.graphics.draw(game.ship.sprite,
                 state.ship.x,
                 state.ship.y,
-                (state.ship.angle + math.pi / 2) % (math.pi * 2),
+                (state.ship.facing + math.pi / 2) % (math.pi * 2),
                 scale,
                 scale,
                 game.ship.sprite:getWidth() / 2,

asteroids/phys.lua

@@ -19,12 +19,10 @@ function phys.update(actor, dt)
 end
 
 function phys.rotate(actor, angle)
-    actor.angle = (actor.angle + angle) % phys.tau
+    actor.facing = (actor.facing + angle) % phys.tau
 end
 
 function phys.apply(actor, force)
-    assert(actor.speed >= 0)
-    assert(force.speed >= 0)
     local ax = math.cos(actor.angle) * actor.speed
     local ay = math.sin(actor.angle) * actor.speed
     local fx = math.cos(force.angle) * force.speed
@@ -33,7 +31,7 @@ function phys.apply(actor, force)
     local y = ay + fy
 
     local speed = math.sqrt(x ^ 2 + y ^ 2)
-    local angle = math.atan(y, x) % phys.tau
+    local angle = math.atan2(y, x) % phys.tau
     actor.speed = speed
     actor.angle = angle
 end

asteroids/test_phys.lua

@@ -26,7 +26,23 @@ function TestApply()
     phys.apply(actor, { speed = 1, angle = math.pi / 2 })
     t.assertAlmostEquals(
         actor,
-        { x = 0, y = 0, speed = math.sqrt(2), angle = math.pi * 3 / 4 }
+        { x = 0, y = 0, speed = math.sqrt(2), angle = math.pi * 3 / 4 })
+
+    actor = { x = 0, y = 0, speed = 0, angle = 0 }
+    phys.apply(actor, { speed = 1, angle = math.pi / 2 })
+    t.assertAlmostEquals(
+        actor,
+        { x = 0, y = 0, speed = 1, angle = math.pi / 2 })
+
+    phys.apply(actor, { speed = 1, angle = math.pi / 2 })
+    t.assertAlmostEquals(
+        actor,
+        { x = 0, y = 0, speed = 2, angle = math.pi / 2 })
+
+    phys.apply(actor, { speed = 1, angle = math.pi })
+    t.assertAlmostEquals(
+        actor,
+        { x = 0, y = 0, speed = 0, angle = 0 }
     )
 end