Physics cursor

/* Physics cursor script by fp, used for most physics parkour worlds. Often combined with the improved Guest cursors script and used with a ratelimit of 0 chars per second. */
keyConfig.cursorUp = "";
keyConfig.cursorDown = "";
keyConfig.cursorLeft = "";
keyConfig.cursorRight = "";
var backpressureX = 0;
var backpressureY = 0;
var velocityX = 0;
var velocityY = 0;
var keyLeft = false;
var keyRight = false;
var keyUp = false;
document.addEventListener("keydown", function(e) {
    if (checkKeyPress(e, "UP")) {
        keyUp = true;
    }
    if (checkKeyPress(e, "LEFT")) {
        keyLeft = true;
    }
    if (checkKeyPress(e, "RIGHT")) {
        keyRight = true;
    }
});
document.addEventListener("keyup", function(e) {
    if (checkKeyPress(e, "UP")) {
        keyUp = false;
    }
    if (checkKeyPress(e, "LEFT")) {
        keyLeft = false;
    }
    if (checkKeyPress(e, "RIGHT")) {
        keyRight = false;
    }
});

function tick() {
    backpressureY += velocityY + 0.7;
    velocityY /= 1.2;
    backpressureX += velocityX;
    velocityX /= 1.2;
    if (keyLeft) velocityX -= 2;
    if (keyRight) velocityX += 2;
    if (keyUp) {
        moveCursor("down");
        var char = getChar();
        moveCursor("up");
        if (char != " ") {
            velocityY -= 3;
        }
    }
    if (!keyLeft && !keyRight && Math.abs(velocityX) > 0.5) velocityX = 0;
    if (backpressureY >= 1) {
        backpressureY %= 1;
        moveCursor("down");
        if (getChar() != " ") {
            moveCursor("up");
            velocityY = 0;
        }
    } else if (backpressureY <= -1) {
        backpressureY %= 1;
        moveCursor("up");
        if (getChar() != " ") {
            moveCursor("down");
            velocityY = 0;
        }
    }
    if (backpressureX >= 1) {
        backpressureX %= 1;
        moveCursor("right");
        if (getChar() != " ") {
            velocityX = 0;
            moveCursor("left");
        }
    } else if (backpressureX <= -1) {
        backpressureX %= 1;
        moveCursor("left");
        if (getChar() != " ") {
            velocityX = 0;
            moveCursor("right");
        }
    }
};
setInterval(tick, 1000 / 30);