HTML5 CANVAS

The HTML5 CANVAS is an new element that has a lot of features.
You can use CANVAS to add vector graphics, build interactive games and even create animations.
This lesson will take you through how to use the CANVAS element in your HTML5 documents, and explain fallback options for browsers that don't yet support it.
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HTML5.JP from here
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fallback plan
予備プラン
fallback position
最悪の場合の代案
as a fallback
滑り止めに
as a fallback position
代替策として
The fallback has to match the config structure exactly.
予備のコマンド（fallback）も、これらの設定の形式に正確に適合している必要があります。