first commit

bird.js

@@ -0,0 +1,30 @@
+const birdElem = document.querySelector( "[data-bird]" )
+const BIRD_SPEED = 0.5
+const JUMP_DURATION = 150
+
+let timeSinceLastJump = Number.POSITIVE_INFINITY
+
+const setTop = ( top ) => birdElem.style.setProperty( "--bird-top", top )
+
+const getTop = () => parseFloat( getComputedStyle( birdElem ).getPropertyValue( "--bird-top" ) )
+
+const handleJump = ( event ) => {
+    if ( event.code === "Space" ) timeSinceLastJump = 0
+}
+
+export const setupBird = () => {
+    setTop( window.innerHeight / 2 )
+    document.removeEventListener( "keydown", handleJump )
+    document.addEventListener( "keydown", handleJump )
+}
+
+export const updateBird = ( delta ) => {
+    if ( timeSinceLastJump < JUMP_DURATION )
+        setTop( getTop() - BIRD_SPEED * delta )
+    else
+        setTop( getTop() + BIRD_SPEED * delta )
+
+    timeSinceLastJump += delta
+}
+
+export const getBirdRect = () => birdElem.getBoundingClientRect()