language-learning-app/frontend/src/app.css

/* ==========================================================================
   Design System: The Editorial Stillness
   ========================================================================== */

/* --------------------------------------------------------------------------
   Fonts
   -------------------------------------------------------------------------- */

@font-face {
	font-family: archivo; /* set name */
	src: url('/fonts/Archivo-Medium.woff2'); /* url of the font */
	font-weight: 500;
}

@font-face {
	font-family: archivo; /* set name */
	src: url('/fonts/Archivo-Regular.woff2'); /* url of the font */
	font-weight: normal;
}

/* --------------------------------------------------------------------------
   Design Tokens
   -------------------------------------------------------------------------- */

:root {
	/* --- Color: Primary --- */
	--color-primary: #516356;
	--color-on-primary: #e9fded;
	--color-primary-container: #c8d8c8;
	--color-on-primary-container: #2f342e;

	/* --- Color: Secondary --- */
	--color-secondary-container: #dde4de;
	--color-on-secondary-container: #2f342e;

	/* --- Color: Surface Hierarchy (light → dark = elevated → recessed) --- */
	--color-surface-container-lowest: #ffffff; /* most elevated */
	--color-surface-container-low: #f4f4ef;
	--color-surface: #faf9f5; /* base */
	--color-surface-container: #eeede9;
	--color-surface-container-high: #e8e8e3;
	--color-surface-container-highest: #e2e1dd;
	--color-surface-dim: #d6dcd2; /* recessed utility */

	/* --- Color: On-Surface --- */
	--color-on-surface: #2f342e; /* replaces pure black */
	--color-on-surface-variant: #5c605b;

	/* --- Color: Outline --- */
	--color-outline: #8c908b;
	--color-outline-variant: #afb3ac; /* use at 20% opacity as "ghost border" */

	/* --- Typography: Font Families --- */
	--font-display: 'archivo', sans-serif;
	--font-body: 'Newsreader', serif;
	--font-label: 'Inter', sans-serif;

	/* --- Typography: Scale --- */
	--text-display-lg: 3.5rem; /* article titles */
	--text-display-md: 2.75rem;
	--text-display-sm: 2.25rem;
	--text-headline-lg: 1.875rem;
	--text-headline-md: 1.5rem;
	--text-headline-sm: 1.25rem;
	--text-title-lg: 1.125rem;
	--text-title-md: 1rem;
	--text-body-xl: 1.25rem; /* long-form reading standard */
	--text-body-lg: 1rem;
	--text-body-md: 0.9375rem;
	--text-body-sm: 0.875rem;
	--text-label-lg: 0.875rem;
	--text-label-md: 0.75rem; /* metadata, all-caps */
	--text-label-sm: 0.6875rem;

	/* --- Typography: Weights --- */
	--weight-light: 300;
	--weight-regular: 400;
	--weight-medium: 500;
	--weight-semibold: 600;
	--weight-bold: 700;

	/* --- Typography: Line Height --- */
	--leading-tight: 1.2;
	--leading-snug: 1.375;
	--leading-normal: 1.5;
	--leading-relaxed: 1.6; /* "Digital Paper" body text minimum */
	--leading-loose: 1.8;

	/* --- Typography: Letter Spacing --- */
	--tracking-tight: -0.025em;
	--tracking-normal: 0em;
	--tracking-wide: 0.05rem; /* label-md metadata */
	--tracking-wider: 0.08rem;

	/* --- Spacing Scale (base-4) --- */
	--space-1: 0.25rem; /*  4px */
	--space-2: 0.5rem; /*  8px */
	--space-3: 1rem; /* 16px — list item separation */
	--space-4: 1.4rem; /* ~22px — list item group separation */
	--space-5: 1.75rem; /* 28px */
	--space-6: 2rem; /* 32px */
	--space-8: 3rem; /* 48px */
	--space-10: 4rem; /* 64px */
	--space-12: 4.5rem; /* 72px */
	--space-16: 5.5rem; /* 88px — top-of-page breathability */

	/* --- Border Radius --- */
	--radius-xs: 0.125rem;
	--radius-sm: 0.25rem;
	--radius-md: 0.375rem; /* primary button */
	--radius-lg: 0.75rem;
	--radius-xl: 1.25rem;
	--radius-full: 9999px;

	/* --- Elevation: Ambient "Tonal Shadow" --- */
	--shadow-tonal-sm: 0 4px 16px 0 color-mix(in srgb, var(--color-on-surface) 5%, transparent);
	--shadow-tonal-md: 0 8px 32px 0 color-mix(in srgb, var(--color-on-surface) 5%, transparent);

	/* --- Motion --- */
	--duration-fast: 100ms;
	--duration-normal: 200ms;
	--duration-slow: 400ms;
	--ease-standard: cubic-bezier(0.2, 0, 0, 1);

	/* --- Glass / Frosted Effect --- */
	--glass-bg: color-mix(in srgb, var(--color-surface) 80%, transparent);
	--glass-blur: 24px;
}

/* --------------------------------------------------------------------------
   Reset & Base
   -------------------------------------------------------------------------- */

*,
*::before,
*::after {
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}

html {
	font-size: 16px;
	-webkit-text-size-adjust: 100%;
	scroll-behavior: smooth;
}

body {
	font-family: var(--font-body);
	font-size: var(--text-body-lg);
	font-weight: var(--weight-regular);
	line-height: var(--leading-relaxed);
	color: var(--color-on-surface);
	background-color: var(--color-surface);
	-webkit-font-smoothing: antialiased;
	-moz-osx-font-smoothing: grayscale;
}

/* --------------------------------------------------------------------------
   Typography Utilities
   -------------------------------------------------------------------------- */

.display-lg {
	font-family: var(--font-display);
	font-size: var(--text-display-lg);
	font-weight: var(--weight-bold);
	line-height: var(--leading-tight);
	letter-spacing: var(--tracking-tight);
}

.headline-md {
	font-family: var(--font-display);
	font-size: var(--text-headline-md);
	font-weight: var(--weight-semibold);
	line-height: var(--leading-snug);
}

.label-md {
	font-family: var(--font-label);
	font-size: var(--text-label-md);
	font-weight: var(--weight-medium);
	letter-spacing: var(--tracking-wide);
	text-transform: uppercase;
}

.link {
	color: var(--color-primary);
	text-decoration: none;
	font-weight: var(--weight-medium);
	transition: opacity var(--duration-fast) var(--ease-standard);
}

.link:hover {
	opacity: 0.7;
}

/* --------------------------------------------------------------------------
   Component: Form
   -------------------------------------------------------------------------- */

.form {
	display: flex;
	flex-direction: column;
	gap: var(--space-4);
}

.form-header {
	margin-bottom: var(--space-6);
}

.form-eyebrow {
	font-family: var(--font-label);
	font-size: var(--text-label-md);
	font-weight: var(--weight-medium);
	letter-spacing: var(--tracking-wide);
	text-transform: uppercase;
	color: var(--color-on-surface-variant);
	margin-bottom: var(--space-1);
}

.form-title {
	font-family: var(--font-display);
	font-size: var(--text-headline-lg);
	font-weight: var(--weight-semibold);
	line-height: var(--leading-snug);
	color: var(--color-on-surface);
}

.form-footer {
	display: flex;
	align-items: center;
	gap: var(--space-2);
	margin-top: var(--space-6);
	font-family: var(--font-label);
	font-size: var(--text-body-sm);
	color: var(--color-on-surface-variant);
}

/* --------------------------------------------------------------------------
   Component: Button
   -------------------------------------------------------------------------- */

.btn {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	gap: var(--space-2);
	padding: var(--space-2) var(--space-4);
	border: none;
	border-radius: var(--radius-md);
	font-family: var(--font-display);
	font-size: var(--text-label-lg);
	font-weight: var(--weight-medium);
	letter-spacing: var(--tracking-wide);
	cursor: pointer;
	text-decoration: none;
	transition:
		opacity var(--duration-normal) var(--ease-standard),
		background-color var(--duration-normal) var(--ease-standard);
}

.btn-primary {
	background-color: var(--color-primary);
	color: var(--color-on-primary);
}

.btn-primary:hover {
	opacity: 0.88;
}

.btn-secondary {
	background-color: var(--color-secondary-container);
	color: var(--color-on-secondary-container);
}

.btn-ghost {
	background: none;
	color: var(--color-primary);
	padding-inline: var(--space-2);
}

/* --------------------------------------------------------------------------
   Component: Input
   -------------------------------------------------------------------------- */

.field {
	display: flex;
	flex-direction: column;
	gap: var(--space-1);
}

.field-label {
	font-family: var(--font-label);
	font-size: var(--text-label-md);
	font-weight: var(--weight-medium);
	letter-spacing: var(--tracking-wide);
	text-transform: uppercase;
	color: var(--color-on-surface-variant);
}

.field-input {
	background-color: var(--color-surface-container-high);
	color: var(--color-on-surface);
	border: none;
	border-bottom: 1px solid color-mix(in srgb, var(--color-outline-variant) 20%, transparent);
	border-radius: var(--radius-sm) var(--radius-sm) 0 0;
	padding: var(--space-2) var(--space-3);
	font-family: var(--font-body);
	font-size: var(--text-body-lg);
	line-height: var(--leading-normal);
	outline: none;
	width: 100%;
	transition: border-color var(--duration-fast) var(--ease-standard);
}

.field-disabled {
	font-family: var(--font-body);
	font-size: var(--text-body-lg);
	color: var(--color-on-surface-variant);
	padding: var(--space-2) var(--space-3);
	background-color: var(--color-surface-container);
	border-radius: var(--radius-sm) var(--radius-sm) 0 0;
	border-bottom: 1px solid color-mix(in srgb, var(--color-outline-variant) 20%, transparent);
}

.field-input::placeholder {
	color: var(--color-outline-variant);
}

.field-input:focus {
	border-bottom: 2px solid var(--color-primary);
}

.field-select {
	background-color: var(--color-surface-container-high);
	color: var(--color-on-surface);
	border: none;
	border-bottom: 1px solid color-mix(in srgb, var(--color-outline-variant) 20%, transparent);
	border-radius: var(--radius-sm) var(--radius-sm) 0 0;
	padding: var(--space-2) var(--space-8) var(--space-2) var(--space-3);
	font-family: var(--font-body);
	font-size: var(--text-body-lg);
	line-height: var(--leading-normal);
	outline: none;
	width: 100%;
	cursor: pointer;
	appearance: none;
	background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%235c605b' stroke-width='1.5' fill='none' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
	background-repeat: no-repeat;
	background-position: right var(--space-3) center;
	transition: border-color var(--duration-fast) var(--ease-standard);
}

.field-select:focus {
	border-bottom: 2px solid var(--color-primary);
}

.field-textarea {
	background-color: var(--color-surface-container-high);
	color: var(--color-on-surface);
	border: none;
	border-bottom: 1px solid color-mix(in srgb, var(--color-outline-variant) 20%, transparent);
	border-radius: var(--radius-sm) var(--radius-sm) 0 0;
	padding: var(--space-2) var(--space-3);
	font-family: var(--font-body);
	font-size: var(--text-body-lg);
	line-height: var(--leading-relaxed);
	outline: none;
	width: 100%;
	min-height: 14rem;
	resize: vertical;
	transition: border-color var(--duration-fast) var(--ease-standard);
}

.field-textarea::placeholder {
	color: var(--color-outline-variant);
}

.field-textarea:focus {
	border-bottom: 2px solid var(--color-primary);
}

.field-hint {
	font-family: var(--font-label);
	font-size: var(--text-label-md);
	color: var(--color-on-surface-variant);
	margin-top: var(--space-1);
}

/* --------------------------------------------------------------------------
   Component: Alert
   -------------------------------------------------------------------------- */

.alert {
	padding: var(--space-3);
	border-radius: var(--radius-md);
	font-family: var(--font-label);
	font-size: var(--text-body-sm);
}

.alert-error {
	background-color: color-mix(in srgb, #b3261e 10%, var(--color-surface));
	color: #b3261e;
	border-left: 3px solid #b3261e;
}