Katakana

In my holiday adventures, though I definitely slacked off in general about learning Japanese, I did do some work while on the plane (there and back!) so I learned a bit of katakana.

Here's what I know:

ア - a

イ - i

ウ - u (this one's easy because it looks almost exactly like う, just squared off)

エ - e

オ - o

カ - ka (same as か)

キ - ki (same as き)

ク - ku 

ケ - ke (why must ku and ke look so much alike?)

コ - ko

サ - sa 

シ - shi

ス - su (this one is everywhere, so it's easy to remember)

セ - se (very close to せ)

ソ - so

タ - ta

チ - chi

ツ - tsu

テ - te

ト - to

So I think these ones are fairly well embedded in my mind, at least in order, but シ, ソ, and ツ are giving me problems... they look way too much alike!