flashcards/theme.css at main · langformat/flashcards · GitHub

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/* ============================================================================
   Theme Infrastructure - Shared across all pages
   ============================================================================ */

/* Shared semantic variables for dark mode support */
:root {
    --surface-color: #ffffff;
    --surface-secondary: #f8f9fa;
    --text-color: #333;
    --text-muted: #6c757d;
    --border-color: #dee2e6;
    --input-border: #ced4da;
    --input-bg: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

[data-theme='dark'] {
    --surface-color: #1e1e2e;
    --surface-secondary: #2a2a3c;
    --text-color: #e0e0e0;
    --text-muted: #a0a0b0;
    --border-color: #3a3a4c;
    --input-border: #4a4a5c;
    --input-bg: #2a2a3c;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

/* Smooth transition for theme changes - applied momentarily during toggle */
html.theme-transition,
html.theme-transition *,
html.theme-transition *::before,
html.theme-transition *::after {
    transition:
        background-color 0.3s ease,
        color 0.3s ease,
        border-color 0.3s ease,
        box-shadow 0.3s ease !important;
    transition-delay: 0s !important;
}

/* Visually-hidden, screen-reader-only label utility (shared across pages). */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Global reduced-motion safety net. Near-zero (not `none`) so animationend /
   transitionend listeners still fire and JS state machines don't stall. Pages
   with richer motion (quiz.css / poll.css) layer their own reduce blocks on
   top of this. */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* Theme Toggle Button */
.theme-toggle {
    position: fixed;
    /* Keep clear of the iOS home indicator / notch when viewport-fit=cover. */
    bottom: calc(1rem + env(safe-area-inset-bottom));
    right: calc(1rem + env(safe-area-inset-right));
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 2px solid rgba(128, 128, 128, 0.3);
    background-color: rgba(255, 255, 255, 0.9);
    cursor: pointer;
    z-index: 9999;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
    transition:
        background-color 0.3s,
        transform 0.2s;
    -webkit-tap-highlight-color: transparent;
    padding: 0;
    line-height: 1;
}

.theme-toggle:hover {
    transform: scale(1.1);
}

.theme-toggle:active {
    transform: scale(0.95);
}

/* Keyboard focus ring — the round custom button otherwise shows only the UA
   default, which is easy to miss on the translucent background. */
.theme-toggle:focus-visible {
    outline: 3px solid #1a73e8;
    outline-offset: 2px;
}

[data-theme='dark'] .theme-toggle {
    background-color: rgba(50, 50, 50, 0.9);
    border-color: rgba(128, 128, 128, 0.4);
}

@media (max-width: 768px) {
    .theme-toggle {
        top: calc(0.5rem + env(safe-area-inset-top));
        right: calc(0.5rem + env(safe-area-inset-right));
        bottom: auto;
        /* 40px keeps the tap target close to the 44px guideline while staying
           unobtrusive in the corner on small screens (was 32px). */
        width: 40px;
        height: 40px;
        font-size: 1.05rem;
        border-width: 1px;
    }
}