The stroke direction is an important factor in distinguishing katakana symbols. The last strokes of ソ ("so") and ン ("nn") are wirtten in the opposite directions as shown on the left. To emphasize the direction of the last stroke, we often put a small hook at its beginning. The following animation may help you associate katakana ソン with hiragana そん.

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Similarly, the last strokes of ツ ("tsu") and シ ("shi") are written in the opposite directions as shown on the left. To emphasize the direction of the last stroke, we often put a small hook at its beginning. The following animation may help you associate katakana ツシ with hiragana つし.

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The angle of strokes is also an important factor in distinguishing symbols like ソ ("so") and リ ("ri") . The two strokes in ソ are slanted inwardly while the strokes in リ are parallel to one another (initially).