:root {
    --primary: #007AFF; /* Apple-like blue */
    --primary-hover: #0062CC;
    --background: #F3F4F6;
    --card-bg: #FFFFFF;
    --text-main: #111827;
    --text-secondary: #6B7280;
    --border: #E5E7EB;
    --danger: #EF4444;
    --radius-lg: 16px;
    --radius-md: 8px;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --font-family: 'Inter', system-ui, -apple-system, sans-serif;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--background);
    color: var(--text-main);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.app-header {
    display: flex;
    align-items: center;
    padding: 20px 0;
    margin-bottom: 20px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--text-main);
}

/* Hero Text */
.hero-text {
    margin-bottom: 32px;
}

.hero-text h1 {
    font-size: 2rem;
    font-weight: 800;
    margin-bottom: 8px;
    letter-spacing: -0.025em;
}

.hero-text p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* CGPA Card */
.cgpa-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-sm);
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 32px;
    border: 1px solid var(--border);
}

.cgpa-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-main);
    margin-bottom: 8px;
}

.cgpa-value {
    font-size: 3.5rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1;
    letter-spacing: -0.025em;
}

#reset-btn {
    color: var(--primary);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    background: none;
    border: none;
    transition: opacity 0.2s;
}

#reset-btn:hover {
    opacity: 0.8;
}

/* Semester Card */
.semester-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-sm);
    margin-bottom: 24px;
    border: 1px solid var(--border);
}

.semester-header {
    margin-bottom: 20px;
}

.semester-title {
    font-size: 1.25rem;
    font-weight: 700;
}

/* Course List Grid */
.course-list-header {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 40px;
    gap: 12px;
    margin-bottom: 8px;
}

.col-name, .col-grade, .col-credits {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-main);
}

.course-row {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 40px;
    gap: 12px;
    margin-bottom: 12px;
    align-items: center;
}

/* Inputs */
.input-field {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.95rem;
    color: var(--text-main);
    outline: none;
    transition: border-color 0.15s, box-shadow 0.15s;
    background-color: #fff;
}

.input-field:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.1);
}

.input-field::placeholder {
    color: #9CA3AF;
}

select.input-field {
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg width='10' height='6' viewBox='0 0 10 6' fill='none' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M1 1L5 5L9 1' stroke='%236B7280' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 32px;
}

/* Buttons */
.btn-primary-large {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    background-color: var(--primary);
    color: white;
    font-weight: 600;
    font-size: 1rem;
    padding: 12px 24px;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    width: 100%;
    max-width: 300px;
    margin: 0 auto;
    transition: background-color 0.2s;
}

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

.btn-secondary-small {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background-color: #EBF5FF; /* Light blue */
    color: var(--primary);
    border: none;
    padding: 8px 16px;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.875rem;
    cursor: pointer;
    transition: background-color 0.2s;
    margin-top: 8px;
}

.btn-secondary-small:hover {
    background-color: #DBEAFE;
}

.btn-icon {
    background: none;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 8px;
    border-radius: 6px;
    transition: background-color 0.2s;
}

.btn-icon:hover {
    background-color: #FEE2E2;
}
.btn-icon:hover path {
    stroke: var(--danger);
}

.actions-container {
    display: flex;
    justify-content: center;
    margin-top: 40px;
    margin-bottom: 60px;
}

/* Responsive */
@media (max-width: 640px) {
    .course-list-header {
        display: none; /* Hide headers on small screens */
    }

    .course-row {
        grid-template-columns: 1fr; /* Stack vertically */
        gap: 8px;
        background: #F9FAFB;
        padding: 12px;
        border-radius: 8px;
        position: relative;
    }
    
    /* Make delete button absolute on mobile cards */
    .delete-course-btn {
        position: absolute;
        top: 8px;
        right: 8px;
    }

    .course-grade, .course-credits {
        width: 100%;
    }
}