If Slope is visible but does not respond to keys, test focus first. If the game never reaches its menu, treat that as a loading or provider problem instead of an input problem.
Click the embedded game before testing keys
Browsers route keyboard input to the currently focused element. An iframe can be on screen while the outer page still owns focus. Click the playable area once, then use a short left-right test on the menu or an open section.
Separate key binding from browser behavior
If an arrow key scrolls the page, the game frame probably does not have focus. If one key works and another does not, try the documented alternate layout. If no keys work but mouse controls inside the game respond, the problem is more likely binding or focus than loading.
Extensions and shortcuts can interfere
Keyboard-remapping extensions, accessibility tools and browser shortcuts can capture input before it reaches a game. Test in a clean window when possible. Change one variable at a time so you know which layer was responsible.
Do not diagnose frame-rate problems as input loss
A heavily stuttering WebGL client can make steering feel delayed even though the keys are being received. If visual motion freezes or jumps, use the performance guide. True input failure and low frame rate require different fixes.
Apply Fix Slope Keyboard Input Problems in a normal run
Practice this topic as a sequence of observations, not as a demand to force the same steering on every generated track. For Fix Slope Keyboard Input Problems, keep the first visible principle in mind: Click the embedded game before testing keys. Then use separate key binding from browser behavior as the second checkpoint, so the test covers both the initial choice and what follows from it.
Before each attempt, state what a successful result should look like. That prediction might be an earlier lane choice, a shorter correction, a wider landing or less sideways drift. If the expected change does not appear, adjust the cue rather than simply pressing harder on the next run.
Judge progress by repeatability. One successful pass proves only that the line was possible; several calmer exits show that the decision is becoming reliable. Once that reliability appears, return to normal score attempts and see whether the habit survives without conscious rehearsal.