function updateGameLogic() {
    if (isCrouching) {
        inputLog.push({ t: currentTick - lastSentTick, act: "DUCK" });
    }

    const originalHeight = 50; const crouchHeight = 25;
    player.h = isCrouching ? crouchHeight : originalHeight;
    let drawY = isCrouching ? player.y + (originalHeight - crouchHeight) : player.y;

    player.vy += GRAVITY;
    if (isCrouching && !player.grounded) player.vy += 2.0;
    player.y += player.vy;

    if (player.y + originalHeight >= GROUND_Y) {
        player.y = GROUND_Y - originalHeight; player.vy = 0; player.grounded = true;
    } else { player.grounded = false; }

    let nextObstacles = []; let rightmostX = 0;
    for (let obs of obstacles) {
        obs.x -= GAME_SPEED;
        const playerHitbox = { x: player.x, y: drawY, w: player.w, h: player.h };

        if (checkCollision(playerHitbox, obs)) {
            player.color = "darkred";
            if (!isGameOver) { sendChunk(); gameOver("Kollision"); }
        }
        if (obs.x + obs.def.width > -100) {
            nextObstacles.push(obs);
            if (obs.x + obs.def.width > rightmostX) rightmostX = obs.x + obs.def.width;
        }
    }
    obstacles = nextObstacles;

    // Spawning
    if (rightmostX < GAME_WIDTH - 10 && gameConfig) {
        const gap = Math.floor(400 + rng.nextRange(0, 500));
        let spawnX = rightmostX + gap; if (spawnX < GAME_WIDTH) spawnX = GAME_WIDTH;

        let possibleObs = [];
        gameConfig.obstacles.forEach(def => {
            if (def.id === "eraser") { if (score >= 500) possibleObs.push(def); } else possibleObs.push(def);
        });
        const def = rng.pick(possibleObs);

        let speech = null;
        if (def && def.canTalk) { if (rng.nextFloat() > 0.7) speech = rng.pick(def.speechLines); }

        if (def) {
            const yOffset = def.yOffset || 0;
            obstacles.push({ x: spawnX, y: GROUND_Y - def.height - yOffset, def: def, speech: speech });
        }
    }
}

function checkCollision(p, obs) {
    const paddingX = 5; const paddingY_Top = 5; const paddingY_Bottom = 5;
    return (p.x + p.w - paddingX > obs.x + paddingX && p.x + paddingX < obs.x + obs.def.width - paddingX &&
        p.y + p.h - paddingY_Bottom > obs.y + paddingY_Top && p.y + paddingY_Top < obs.y + obs.def.height - paddingY_Bottom);
}